Thanks for all this advice but i still don't know what PNG is and is the GIMP thing free? Sorry for all these questions. I'm a beginner (at drawing).GIMP is GNU Image Manipulation Program. It's a free sort of alternative to Photoshop and other expensive graphic programs. It's not as good, but it's helpful for those of us who don't want to spend money on a program.
The Eevee could have been turned into a sprite if it wasn't jpeg. Always save as PNG, since anything else will destroy the details.
On the other two, your lines are shaky. If you choose not to turn them into sprites and keep the outline more than one pixel thick, it's hard to erase and fix the lines when you mess up.