Few tips for ya. :)
I think instead of drawing Sugimori's Decidueye or Greninja, you should work on drawing your own! We'd much rather see how you interpret these Pokemon since we already know what the GF artwork looks like. I think you should work on having a background too! It doesn't have to be anything too crazy, just some nice colors or a simple gradient, but something to bring the composition of the whole piece together a little more. Lastly, work on integrating your text into the piece better. Right now it feels very separate from the artwork and I believe those two elements can work well together (like in your avatar!). You've got a good base for a wallpaper going here, and I think will just a little more TLC you'll have something really special on your hands. Just keep at it! :)