I like to use my own photos and sketches whenever possible.
I used the snowflakes from a photo of our garden in December 2009, the week the local school children were given Snow Days off.
I roughly photoshopped the snowflakes onto the polar bear picture.
I then needed 3 different blocks for the different colours I wanted, taking into consideration the colours produced by the different blocks printed on top of each other, so I started by printing off 3 black and white photo copies.
I find it helpful to paint the areas to be printed, as you can see in 2 of the photocopies below.