I agree the most with his last statement, things that you like, that are compatible with this size tank.
All of reefer1024's ideas are great for variety and color.
The sexy shrimp are a blast to watch, low bioload and are in constant movement-- and don't jump out of tanks;
small goby's are great. For many species, in a tank this size, if you don't actually get a mated pair, one will kill the other.
Frogspawn are great for movement, but can grow quickly (like tripple in 6 months) and overwhelm your tank;
Blasto's and micro's can add lots of color and not overgrow your tank for a while;
Ricordia yuma's can often be very tempermental-- especially the more brightly colored ones. I wouldn't even consider one until your tank matures at least 3 months.
Ricordia florida can offer great color and texture with less chance of loss and are much less expensive.
Then again, reefer has been doing this 7 years and me 7 months, so this is just my experience and what I've learned so far.
Good luck. Very interesting build. Been fun watching your thread and remembering all the questions I've had.