@ravanon@mastodon.scot readability of sprites over backgrounds is probably the hardest part of pixel art. I've been doing it for over 25 years and I still struggle with it. If you wanna remove the black outlines for the sprites, but retain readability, I'd suggest either using highly contrasting colors between the characters and the background tiles or lowering the saturation of the backgrounds just a smidge relative to the character sprites. You can also keep and change the sprite outlines to color match each character. Say, for example, a character has a lot of blues, then give it a dark navy blue outline.