It was simply made for the fun of it, actually. And never to throw it in.
Since that is the purpose of the mod and the game, is it not?
Of course, if you don't to see this mod anymore. Then I'll remove Blue completely off the list.
Whether you made it for fun or not, you modified another author's work and published it in a public space. You're not the first person to make this mistake, but you're one of the first who has hasn't taken the effort to ask for permission after the fact.
If you had apologised and asked for permission it would likely have been granted. You have not abided by common courtesy or basic manners, let alone legally enforceable copyright laws. If you don't ask permission and you are asked to take it down, then you must take it down otherwise a site moderator will be forced to do it for you.
Copyright is a serious issue, authors on this site spend hundreds if not a thousand hours or more creating their ship assets, and stealing someone else's pixel art just isn't cricket mate. It is completely disrespectful to community members to be copying their work without their permission. Disrespecting one content author and continuing to flaunt that you take art without permission is tantamount to saying that you believe everyone's work is free for you to use without explicit permission, and you therefore disrespect every artist in this community in your actions.
I suggest rectifying your behaviour immediately, and removing the infringing ships until such time that permission is granted.