As a developer I know one of the hardest parts about developing games on my own is the fact that as an artist I'm completely shite. Thankfully, there are a lot of public domain art sources which can help get one up and running quickly. Still, placeholder art isn't really art, is it?
The folks behind the Indie Graphics Builder asset set reached out to me to let me know about the release of the Indie Graphics Builder, or IGB. I have to say, it looks great. The price is too high for me, personally (it is $199), but a small studio with minor funding (or perhaps with some Kickstarter cash) could definitely spring for it.
I won't bore you with all the details (they have a website for full information), but take a look at these two videos to get an idea of the kinds of things you can do with their art sets in photoshop just by piecing them together with one another.