I'd never put real plants on real wood unless you know how to remove something called "iron gall ink" stains from wood. Generally a yellowy or reddish colour most often indicates the wood has a lot of tannin in it, like cedar, redwood, red oak, Douglas fir, southern yellow pine, etc. Putting a real plant on a high tannin wood is courting disaster.
The reason why is that if you overwater the plant, and any water drips out of that pot, it won't be distilled water. It'll have iron ions in it from passing through the soil, and the iron ions in that water will react with the tannin (also called "tannic acid") in the wood to form something called "iron tannates" which when dissolved in water form "iron gall ink" which was commonly used from the beginning of the middle ages (1100ish) until the 1800's.
http://en.wikipedia.org/wiki/Iron_gall_ink
Iron gall ink will penetrate into wood just like a wood stain, and bleach won't remove it, only lighten it to some degree. You can only remove it using acid. A dilute solution (about 3% concentration) of either phosphoric acid or oxalic acid will dissolve the iron tannates and leave behind colourless iron salts, thereby removing the stain. You can find phosphoric acid in the cleaning aisle of any home center as it's commonly used as the active ingredient in bathroom cleaners and toilet bowl cleaners because it cuts through soap scum without attacking chrome. Oxalic acid is typically sold as "wood bleach" and is used to remove the gray discolouration that occurs on wood exposed to the elements. Oxalic acid is therefore used to clean up old wood that's been stored outdoors prior to using it in an application where you want the wood to look unweathered, and any hardware store that caters to woodworkers should sell it.
The problem of iron staining on high tannin woods is so pervasive that even wood transported on railway cars can often be stained. Tiny iron particles that come off the steel wheels of the rail cars or the steel rails they roll on can land on wet wood and result in discolourations due to iron tannates forming ink and being absorbed into the wood.
http://web.archive.org/web/20060423125820/www.durable-wood.com/pdfs/discolor_eng.1oct02.pdf
There's been more red oak hardwood floors ruined by overwatered plants than any one other cause, and in most cases the stains on those floors were never removed because the home owners only tried bleach (unsuccessfully) in an attempt to remove the stains.
If you're going to put real plants on those ledges, either don't use real wood or let the plants die of thirst. Truthfully, the real solution is to use a wood with a very low tannin content, but I simply don't know which woods those are. That's because it's the tannins in the high tannin woods that cause all the problems. So, you hear about the problems that tannins cause in high tannin woods, but nothing about low tannin woods where there are no problems.
If it was me, I would probably install flourescent or recessed lighting on top of those ledges so the light reflected off the walls and ceiling and illuminated the whole room. Install glass or strong plastic covers over fluorescent light fixtures or install recessed lighting in laminated particle board boxes, and then you can put whatever you want on top.
Just a thought. Occasionally I think.
