Hmmm... in terms of putting a a profile picture, whether it's your gender or your opposite gender, I think it's personally fine. When I was younger, I did have a similar feeling to as you feel. Though in my case, I thought I had to have my real face and real name on stuff.
However, in the past I had my email hacked by one of my close friends that I know in real life. We went to the same school and we knew each other for many years. They impersonated me in a way that negatively affected my reputation, and they even could have tried to target my family. Maybe the damage was already done. I forgive them and love them, but, my goal is to prevent damage like that from being caused.
Now I try to purposely avoiding revealing real life stuff about me. Rather than my real face profile picture, for stuff like this, I just keep it as a Bible verse. With deep fake technology now, who knows what malicious actors could do with my face. I have many enemies after all, both in real life and online. I have enough people who want to hurt my family as is.
That's why I'm personally fine when people have a profile picture of a different gender. I have made accounts with profile pictures of the opposite gender before, like with Touhou characters.
So in terms of having the opposite gender as your profile picture it's good for the following:
I use different names online. Not all of them are my real name. I do this to protect the safety of my family. So having a profile picture of something else rather than yourself that you like helps this. For secrecy though, if you have a Yuuka profile picture on everything, they might trace that alternative account back to your main account. So it can be useful to have different styles of profile pictures. Same gender, opposite gender, variety in general is good for being anonymous. These security measures can be "spiritual walls" in a sense.
Psalm 122:7 Peace be within your walls and security within your towers!”
A Touhou fan may be more likely to listen to a Christian with another Touhou character as their profile picture. It's like how Paul would be relatable like a Jew to other Jewish people, even though he was a Christian under the Law of Love and not forced to obey like all the Leviticus Laws (though would still be compelled to maintain the Lord's Law of Love)
1 Corinthians 9:20 To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law.
Like on social media sties, I find that maybe sometimes people are less prone to talking to people with default user accounts because they might believe they are talking to bots. Truly I tell you, sometimes when using the default avatar, people have asked me "Are you a bot" multiple times. Having a profile picture can be a good way to have people listen to you more.
I have dozens of alternate accounts for particular websites. It can be tricky to remember all of their names, so a profile picture of something unique is a good way to make it memorable. Like an anime girl, a fire hydrant, or a stock image vector logo.
As well, it helps me remember which account I'm using. Many Christian forums look quite similar and I have the same username on multiple, but I have different Bible verses on each and profile pictures. So looking at that photo helps me to know which account I'm using.
Psalm 77:11 I will remember the deeds of the Lord; yes, I will remember your wonders of old.
Based on these, that's why when I'm online, I usaully refer to people as "they" so it's gender neutral. I don't know if someone's a boy or a girl. I don't want to offend a girl by calling them a boy, or offend a boy by calling them a girl and vice versa.
I remember in a Discord server once, I was talking to a person with an anime girl as their profile picture and I thought they were a girl when talking to them, but they later revealed themselves to be a guy. I think someone even pinned that interaction. Now I've begun to notice that... oftentimes there are girls who have anime boys as their profile picture and boys who have anime girls as their profile pictures because they really like the character, and I don't see anything wrong with that concept. Certainly I have had a Touhou girl as my profile picture because I really like her character.
I also remember when my younger sister who is a minor was on the MMORPG AdventureQuestWorlds (AQW), she had a female avatar and someone privately messaged her asking for her real life phone number then later talking about real life location. I went over to her and was able to protect her from this danger. But I can undersand why girls have profile pictures of guys, in order to protect themselves from getting harassed like that. Though I also have an account on there that looks like a girl.
Another friend of mine was playing a Roblox obby, and they saw someone was saying inappropriate things to them in the chat because they thought they were a girl. So if you have a profile picture of a girl, that sort of behaviour is something you have to watch out for unfortunately Though I have had a Roblox character that looks female when spreading the Gospel on Free Draw.
Overall, I look forward to the day when all people are treated with respect, no matter what gender they are... That's why I find it's easier to call everyone the pronoun "they" because it's tricky remember everyone's genders. I try not to unnecessarily offend people so that they can undestand that Christian truth, that Jesus will save everyone permanently and to believe in Christ the Lord. Naturally, I will offend people. When I see a muslim or a jewish person when evangelizing, in kindness and gentleness, I tell them "Jesus is the only way to Heaven". A necessary offence.
So overall, if you want to put the Yuuka profile picture back up, I'm personally fine with it. Of course, it's your personal choice, since it is your account. But I think it can be useful to have at least some type of profile picture. The Lord of Host's blessings to you my friend
[they reply, so thus I reply]
Oh, that's what you mean. Well, I think it depends on the conditions of the heart. For me when I saw that profile picture of Yuuka I just saw it as a picture. But for you, you may see it differently.
Matthew 5:8 “Blessed are the pure in heart, for they shall see God.
The same goes for profile pictures. So really it personally depends how you feel.
1 Samuel 16:7 man looks on the outward appearance, but the Lord looks on the heart.”
For me, in this scenario, I can look at the outward apperance. It's harder for me to personally see what is in the heart. Since you can see in your heart, it will be best for you to decide. I can only really answer based on the outward appearance of a profile picture. It's up to you whether you want to use Yuuka as your profile picture or not based on how you feel on the inside.