An easy technique today -- Thumping!
Basically you just ink up your stamp (here I used Pumpkin Pie) and then take a marker (Chocolate Chip) and tap the side of the marker on top of the inked stamp to create a spot of a different colour. Do that all over the stamp in one or more colours (I also used Dusty Durango) to get a bunch of different coloured spots. Then huff on your stamp and stamp on your paper.
Gecko. I used watercolour paper and also misted slightly with water so the image would run a little:
Gecko and die cut him into puzzle pieces that I scattered around.