There is lots of work on "artistic rendering" like yours, from the early 1990s to the present. It started with work by Paul Haeberli at SGI [1]. The first chapter in "Image and Video-Based Artistic Stylisation", edited by Paul Rosin and John Collomosse [2] describes many techniques you might be interested in. Have a look; you will like what you see.

1.http://dl.acm.org/citation.cfm?id=97902

2.https://books.google.com/books?id=YjXlTPFYGEYC