Great start! The armor, JP, jumpsuit and bucket look good. Two things that jumped out at me were the forementioned butt armor and the blaster stock. The butt armor is a fitting issue that you should be able to take care of with some elastic or velcro. However, the blaster should be upgraded. Those hollow stock blasters realy throw off the look.
One final nit-pickey item, is the shoulder ribbing on the vest. There seems to be too many ribs, and each rib appears to be a tad small.
Like others have said, nice job for your first attempt. 
Gator