I'm going to echo what a lot of others have been saying, you need to start on a much simpler level. It seems as though you're trying to mesh both pokemon parts as well as re-color, and because the merges aren't consistent and the values aren't the colors appear flat and don't work well.
Doing re-colors will help you get the hang of using color and how to apply it to the sprite, doing simple merges, such maybe adding wings or ears first then work on learning how to get those smaller parts to work with the rest of the body. And don't re-size the part that you are working with, this makes it look distorted.
Once you start getting more comfortable with merging parts and making a good pallet, then I would get into the more complex things, by then they should be much easier to merge and look a lot more like they 'belong' together.It'll take a while to get used to, but once you do, splicing will be a lot more fun and will turn out a lot nicer.
