I would recommend you find… well, there’s a whole list of things I would suggest you do.
Firstly, y’need some good maps man. Construct isn’t meant for pretty pictures, it’s meant for building ugly and dangerous diesel-punky machines. Stuff like this, and this.
Secondly, as with maps, you need good models. Now, you can do what you want, but it’s good to keep a varied pallete or else you can only do so many things. This section should help you out, but don’t just make a thread asking for some pretty models; you’ll have to look around for them and find something you want to work with.
Thirdly, you should probably get GIMP. It’s free and fairly easy to use, so you can edit your pictures as much as you want.
Fourth, and most importantly, POST PROCESSING. It should be a tab just above the tools one, and in there you’ll be able to fiddle about with various effects. It’s super-simple and you can make brilliant filters pretty easily, as well as enable various other effect like bloom and super-DOF.
Also, be sure to check out the sticky. It’s got some neat tutorials that should help you get started. Remember, though: before you take a picture, ALWAYS turn your graphics up to full. It’ll make it look reasonably good no matter what you’ve done, though obviously not as good as it would be with everything else listed here.
Follow this advice and I’m sure you can produce something a bit more worthwhile.