some general notes, with the disclaimer that this is only my opinion and should be taken as such and not some sort of commandment. also, i think most of us could work on these points. i'm sorry if i'm blunt, it's just my style and not a reflection of a harsh view of your work. it's very good, and you've got a lot of talent and potential.

1st - if you're using poser, export your renders as png's if you want to use the character independently of it's background because then the background will be transparent and you won't get the cloud effect. it makes it look like you a) don't have the skill to remove it and b) don't put enough time and effort into your work to get rid of even glaring errors. i can tell from other aspects of your work that you do care about your work, but to me halos say "i'm a complete newbie who just slapped something together," and i have to supress that feeling to get the impact of the good aspects of your work.

2nd - try planning out your pictures. because right now they're rarely really out there in terms of content (except for the latest, you can find tons of nearly identical content in the gallery - standard military vehicle shots, fighting, etc.). conversely, the composition seems random and lacks coherence. if you sketch out ideas before hand, you might find you think through the relationships between elements more thoroughly. where is the gun pointed and why? where is that characting looking, and what are they looking at? right now it's not clear what we're looking at.

3rd - work on lighting. again, make it clear what you want to emphasize, where you want us to focus. lighting also sets mood. i'm not sure what feeling you mean to convey or what you're trying to illustrate. do you want people to go "wow, cool vehicle!" or "that looks exhilarating!" ?

4th - plan out your color scheme. in some pictures (mostly earlier ones), i'm again not sure what sort of look you're going for. they don't exactly vibrate and they don't complement each other. again, you seem like you're playing around, which is great for learning. this isn't to say you can't get wild with your palette, just try to choose your colors with more visual coherence.

and just so you know, i do have actual renders, just not any posted here. i'd like to have my own site ready before having a gallery here. and the only reason i added this statement is exactly the attitude described above. most of the time any criticism is deemed disloyal at best and trolling at worst. usually it results in (fairly personal) criticisms of the original poster's gallery (if they have one), or their comments are completely dismissed if they don't. very few people here take criticism well. i say this from observation- i know my style is far too blunt and normally wouldn't comment in any case. again, i think your work is very good, and that most gallery pics could be improved in above ways.