I'm going to put the image in so it's easier to list it all.
First one: You need to recolor the head and belly.
Second: Any sprites older than S/R/E are bad for spriting nowadays.
Third: Recolor the non-Gyrados parts.
Fourth: Remember to recolor the outline.
Fifth: Bleh... Recolor recolor recolor...
I'll do more when I get back.
Well, to really make it short, just recolor the parts to make them fit in together, remember outlines, and for things like eyes and stuff that don't fit... For example the Regice/Gastly... You can do something like this(I'll just do your sprite and modify it):
I'm sorry, it's a bad example because I'm not sure how the outline of the original sprite without the eyes was.
By the way, they're called fusions.
Other than all that, these are pretty good ones. Keep it up.
Oh, my favorite is probably the Tyranitar/Walrein mix(they can also be called mixes, those are just the two most common names).
Oh and one more thing. You need to shade. ;)