This is my entry for the Mythical Creature Challenge.
This was created as a vector using Inkscape. I've changed the colour scheme to suite the purple shirt better. The link for the original is here [link]
I used only 5 colours even though it looks like I used 6. My trick was to cut holes in the design/image so the colour of the T-shirt would show through.
When I was creating it I use a background that was the same colour as the t-shirt I originally designed it for. This way I could see what the image would look like on the colour with shapes cut out.