Here's some Classic Space Figures I did in Photoshop:
I've also posted these on Cuusoo. (I could care less about the supposed money, I just want the figures so would love for them to get the support)
As for tips: Not sure who is interested in Photoshoping figs (as opposed to actual customizing) but it's fairly easy to do stuff like this. It's mostly a matter of taking two figures in similar light and merging the images. If anyone has any questions let me know.