Sketch: Moscow steampunk (4000 x 3000)
Prints available at Artist website (mirrors at Pixels and FineArtAmerica), RedBubble.com.
Licenses for commercial use - at Shutterstock.com, 500px.com.
I've tried nice program PhotoSketcher and really like it! It is free, have lots of painting modes and settings, and produces very interesting results. I definitely will use it more.
From this HDR photo i created in PhotoSketcher 5 variants with different level of details (different number of passes and minimal brush size). Then, i combined them in Photoshop with masks, and applied canvas texture from this great set: free canvas textures.