In menu bar [ Window>Rendering editors>Hardware Render Buffer ] will render out wireframe. You may have to set some options in the attribute editor.
To get a transparent background save as .iff
Working with adobe you would think .tiff but I beleive it leaves a white background in maya.
If you did an intensive render you could always delete all the background in your secondary program.
I found out how to get rid of the black background when saving a maya file as an image file,.........though I'm guessing most of you won't be needing to know this.
What I did was to save the maya scene as an .iff file, then I opened it in fcheck and saved it as a .tiff, then opened it up in windows picture viewer and save it as a png then the background becomes transparent when I opened it in photoshop!!
It's a bit of a process, and if anybody knows of a single button trick then feel free to email me :-)
You can find on your Photoshop install disk a .iff plug in. It will allow you to open the .iff file directly into Photoshop.
Just render out the .iff, open Photoshop, then just open the .iff directly into Photoshop with the transparency. Once in Photoshop you can save it anyway you like. Post any problems & version Photoshop if it's not working. Good Luck