I think it's possible. Just did it in 'Dark Avatar' and the game even stayed MetaVerse-legal. I can't say for sure in DL, but simply check out the installations-folder where the other pictures are - and replace one with your own style. You'll most likely need to match the height*width of this pic, and have a transparent background, too.
However, don't know if there are more easier solutions. I'm not a modder at all. But hope this helps you.
