That looks... awful, to be honest. Not trying to be a dick, but it looks like all tuxpi did was add a sobel effect and sharpen to a ridiculous degree.
Fotosketcher is a much better program for converting pictures to paintings. Fiddle with the settings a bit and you'll get some neat results.
He most likely used Foto Sketcher to make it. Here is one I made just now using it. Really simple and I suggest using the portable version so you don't have to install anything.
That looks like the oil paint filter (adobe removed it in CC 2014) but I like this one more anyway. Interface sucks though.
You could check commercial plugins like topaz simplify, Fractalius or go grazy and play with Filter Forge.
There's also free stuff like g'mic(gimp) and FotoSketcher that can do amazing things.
reading the other comments:
If you are going to take a poor quality original and convert it to a painting, then enlarge it to a decent size, make corrections, etc.
They you can apply your painting effects as appropriate.
Here is something using the painting effects from FotoSketcher. I changed the jacket color in Photoshop
When you enlarge it, you can get enough subtle texture to make it interesting
The story is really interesting. I think the requirements from the artists are a bit of a tall order. Do you live in the UK? I recommend taking pictures yourself and using a filter like this for your backgrounds: http://www.fotosketcher.com/ I'm pretty sure there's zero free background artists since it's the rarest skill set for artists.
I don't think any artist wants to do research on a volunteer project, so you should make it easier on them by giving them the research material to base it off from (or pay them enough to be willing to do it). Also a semi-realistic artist is harder to find as most interested in VNs tend to have a strong anime style. For the time being, use free sprites as the placeholders (you'll need to do it anyway): http://lemmasoft.renai.us/forums/viewforum.php?f=52 Once you have a convincing demo with lots of the assets in place, you'll probably have an easier time in getting an artist (or enough material to make a KS pitch I suppose).
The technique above is great, I use it often and sometimes if im aiming for a more abstract feel I will use fotosketcher http://www.fotosketcher.com/ its like multiple photoshop filters but much faster and can add some nice effects to an image. This usualy always helps if your using stock sketchup textures.