I think the biggest issue is that the edits are much too flat.
I think it would help if you tried to add some variation to the colour to better intergrate it with the standard of the real sprites. It might help if you use a thinner brush, or maybe focus more on the pixels with the pencil tool.

I've been dabbling in sprite edits a little lately, so I can appreciate the effort, but drawing flat on top of sprites always kills the mystery.
I actually think the background's got more going for it, even with the cheesy lens flare (which I love!).

Try to add texture , detail , and sharpness on some of your edits then maybe this would be good photoshop image . 6/10 .

Scorpions torso and everything at the top looks okay, but below the waist doesn't look good. You should add more colors. The other sprite is the same way. You should zoom in and add small colors so it looks pixilated, rather then looking like it was made using solid colors in paint. I don't know anything about photoshop though.

Both of the sprites look too catoonish. Because you said that this is your first time making a fake on Photoshop, I will say it's a good start. Even though you do have a lot to fix, it's not bad for a first try.