i used piskel for pixel art before for a while, then i switched to paint.net, for a long time i made my art on .net and then, then i got aseprite, . now i use aseprite so much whenever i do any stuff on paint.net or piskel it just seems so strange and hard to do stuff (even though i had previously mastered both programs)
ive not used gimp before but i think its better suited for high res textures, like making a grass texture seamless and stuff.
also can we see some of your Artwork?
Cheers!