Not bad. You wanna watch for jaggies, as they can really mess up the look of the image. Transparency is also a big thing with sprites. Not having a transparent background can mean the difference between good and bad.
Bronzong/Nuzleaf - 6/10 You've got some jaggies and what seems to be discoloring near the legs
Dragonite/Victini - 5.5/10 Jaggies on the ears and wings. Shading with the ears doesn't match with the rest of the body too well. The eyes could use a little work.
Mirror Eevee - 8/10 Glasses could use some work, and there's some slight jagging going on around the top of the afro.
Togekiss/Flygon 5/10 - You've got a lot of jaggies going on, and some issues with color transitioning. The Lugia wing tips look really odd, and the legs look like a huge collection of jaggies.
Room for improvement, but not bad at all. My brutally honest review.