This vellum technique is called debossing.
It gives a raised image you can feel, and when you use vellum, you get white highlights as well. I saw a great card at the Spring Fling event using cardstock and the Bloomin' Beautiful set from the Occasions mini.
This is the hostess set From the Garden. I coloured on the stamp then stamped on the vellum. Then I cleaned the stamp and put the vellum back on it, lining it up. I used the tip of the dry embossing tool to trace in between the lines, over the spaces in the rubber. That's the debossing part!
Then on the right side up, I coloured in with markers and used a blender pen to move the colour around a little.
I did get this idea from SCS, but do not remember from whom. If it's your card, I'll gladly give you credit - just let me know!
Happy stampin' and blessings, Ann