Can't stand purists myself. I figure that if it's legal, it's legitimate. As long as you aren't stealing someone else's work, you should do whatever you want. Also, I agree with AS. I don't think any professional will show off a straight render, unless he/she is displaying a 3d model. Photographers are the same. Not doing postwork for digital photography is like letting Wal-Mart develop your film instead of learning how to use the darkroom.

I've been practicing a new technique for painting over renders. A few contrast adjustments or HDR processing to my renders usually satisfies me, as far as renders go. But lately I've been wanting a look that is painted, with visible brush strokes. There are plenty of filters to add such strokes to an image, but they always look fake to me, like no human would ever paint that way. So now I just actually paint over renders. I've become very picky about what kind of photoshop brushes I use. :D

For a large image of about 9000 x 5000 pixels, it takes FOREVER if it's detailed. But I find it almost like meditating, and painting like this is positively addictive, so I don't mind. Also, I can render an image with very low render settings at a preview size (takes about a minute, with IDL, usually) and then just enlarge to whatever size before painting. May need to sharpen up the image a bit first, and lots of details may be lost. But I've discovered that if you try to paint in all those details over a full sized high quality render, the end result looks exactly like a render unless you look at it very close-up. So, for me, upsizing works just fine.

Here's a small cut-out of one I've been working on. The actual image includes a lot more scenery and is much larger. Still need to work on the details -- her hair looks stringy and needs to be painted over again, for instance, and the shadows under her nose are too intense and so on. But I kinda like the overall effect.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.