hey, you definitely have the right idea and feel down - solid concept here. the scheme of the banner is proper, you're working on blending colors in the cloth, the freehand shows dedication to doing the damn thing, and the white lower legs say you see the importance of unique minis in an army.
good, now keep up the practice! a few constructive comments on maybe somet hings to work on:
1. go lighter on your metallics, drybrush - don't apply as thick.
2. do many thin layers of white, it will turn out less gloppy and thick looking.
3. work on being able to mak thin, controlled lines. This will come in handy to add highlights to that armor - which alone would bump up the score of this many to a 4 or, if done well, 5 - and give you other options, like more details in the eyes and even painting scribbles on the your marines purity seals.
keep me posted on your new work! can't wait to see it!.