UPDATE 7/10/2009
I'm collecting crackle textures in a flickr set.
/ UPDATE
A little crackle medium, available at most art and craft supply stores, can give your digital paintings an aged realism.
Lay out a layer of white acrylic paint onto a surface you don't mind ruining, and apply crackle medium according to the product instructions.
When the acrylic paint shrinks, it will crackle as if with age.
Use your favorite Photoshop blend modes to work the cracks into your digital paintings. For the skull example below, I didn't do too much more than just multiply, one image by the other. If you put more time and effort into combining your crackle paint image with your digital painting, you can achieve extremely realistic results.
You may even find the patterns useful in 3D CG for creating things like sun baked mud.
It's a handy texture to have around. I even used it in the banner at the top of this web site.
I took of photo of an old piece of painted siding that I use for exactly this purpose.
Interested parties may download it by clicking here.
The commentor above is the very talented artist Brian "Balistic" Prince. Click on the link to his name in his comment above to visit his site.
thanks for stopping by, Brian!
It's a great site you've got here Joseph. It always gets my neurons firing.
I'll try to swing by more often.
You can also use things like Vaseline and white glue under the acrylic paint,the Vaseline is really good if you want to make large crackle.
Very cool; good to know. I'll try it.
Thanks, Shyla!
(Check out Ugly Shyla's art dolls at http://www.uglyart.net/ )