The head design on the first one is cool, but it looks like you got lazy with the eyes... Also consider using some different parts for the armor. Experiment with the parts, and remember that you don't have to use only captain parts.
As for the second ones, I really like the use of weapon parts. But once again, the armor is too uniform and needs some variation. In both creatures, the coloring is very bland and could be improved.
Sorry if that sounded too critical, I was just being a pessimist and focusing on the things that could be improved. I hope my advice helps.