You might want to check DoGA CGA. It is a Japanese program, but it has options for English menus. In a nutshell, it is 3D toybox of parts that you can color, position, rotate, and scale.
The program comes in three versions, all shareware, but essentially free unless you want to make movies. The versions are called L1, L2, and L3. Lesson 1, gives you the basics, L2 is more advanced, and by the time you hit L3, you have almost full control of the parts, can add more, use custom textures, etc.
It's a pretty easy program to get started with and after a little practice you can create some pretty neat things. with it. L3 also has some rendering options so you can do 'realistic', anime, or manga style images.
Would be glad to walk you though the basics if you're interested. I also run a Yahoo group if you want an English speaking support group for DoGA.
Translated download page: link
Yahoo Group: link
Some stuff I have done: link
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TAZ
(This is posted with the intent to suggest a do it yourself way of making models and images. Not interested in being a concept artist, but would be happy to enable you to create your own neat ideas.)