Are you planning to put any type of sand bed in there?
Basically, I would think you would want to put in things that will eat your nitrates, phosphates, detritus, etc. Items that are normally found in reefs, but do not look attractive in the main tank (such as the macro algae listed above) are great candidates. I have been told by others vastly more experienced than I that its a good place to stick a pod factory, live rock for extra bacteria growth, and other unsightly stuff that will 'clean' the water in a more natural way. Given it is typically out of sight, it can look nasty as you need it and provide benefits to the main system.
I do not have an practical experience myself to share with you on this, only what I have been able to pick up along the way and through research - I am still building my refugium.