Your coming on great MG, its just fine tuning thats needed, Keep at it!
Your stuff is much better than my early work, you know it took me quite sone time to 1st get my head around photoshop then find the patience to sit there & learn from them, (bull & china shop springs to mind of how i was then!) once you have cracked the depth aspect and how to use textures there will be no stopping you.
Saskia aka Fintro has posted a fab tutorial in the relevant section, depth is something which can be difficult to explain but easily taught, if that makes sense.