Charcoal Rubberband Brushes

I'm just getting started & experimenting with my first 6 brushes.  I'm not using the full version of photoshop right now (just PS Elements) so I'm wondering if I should save these as transparent PNGs or just wait to get the full PS to save them as ABRs.  Using the brushes for a border

Testing out different colors/layouts for screenshots.

I decided it was time to to get the full version of PS (Adobe has a $9.99/mo deal through the end of March).   So I added all 16 of my brushes to complete this set.   I'm hoping they have enough contrast- They seemed to look flat when I made them too high contrast.