Measure, snap a line, check level, tape (optional, depending on how good you are with a brush), paint. Vinyl or paint will hold up well, paint is cheaper.
Use a good masonry sealer on the brick/block before you paint. Add a few strong backs to the joists and you'll be fine, just don't store any hemis up there. In your case where the 2xs are nailed on the flat across the joists, you would add another 2x on edge and nail it into the one laying flat...
There's a lot of great shops on this site. Everyone has different ideas and needs. That said I love the old style fillin station builds and some of the monster shops and a few in between.