I just love Mason jars. There are so many cute uses for them. I've had the mason jar stamp set from papertrey ink for a few years, but just pulled it out to make some cards. If you want more card ideas, check out my pinterest board here... http://pinterest.com/jenni_swenson1/paper-crafts/
You can buy the mason jar set here... https://www.papertreyink.com/stamps/friendship-jar-fillers-stamp-set/
I made a background for the paintbrush card by coloring a piece of white cardstock with copic markers.
I love the simplicity of the flowers in a jar too...