How to post a sprite that will fit the theme?

[Silverthorn]

@Phil: that face is somehow creeping me out xD

You cannot upload images whose background changes with the theme. The only possible solution would be to program something in a server-sided language (php, perl, and the like) that'll parse the currently used theme and adjust the background accordingly. But that is pretty awkward

That's why it's usually enough to just pick pre-defined stuff. I personally like to put a sprite on a complementary colored background and on a transparent. Simply because a black BG might take away details if you tend to work with darker values. And white gives makes the contrast between sprite and background too strong to pay attention to the details