Adult coloring book/ cards/ pages have become quite popular. It seems everyone is rediscovering their love of coloring. It's definitely relaxing. Something that we, stampers, have known all along. We've never stopped coloring, but it's nice that now we have so many options besides just coloring our stamped images.
There are many resources for free printables. This one, that I have colored, is one of my favorites. The artwork is by Valentina Harper. You can print it ------> HERE. I like this option because you can print them on whatever paper you prefer.
There are also sellers who have wonderful designs for purchase. I did a quick search on Etsy and found over 4,000 items ------> HERE. Again you have the luxury of printing on the best paper to suit your coloring medium.
There are amazing books available in book stores as well as online. Some of my favorites are: Animal Kingdom by Millie Marotta and Geometric Patterns by Lisa Congdon.
Finally, while you're placing an order for the latest stamps and dies you could toss in some cool coloring cards or books!
OK, I'm headed out to buy a frame to hang this one in my craft room!