That's one of the problems with those Reptariums - they don't let much light through.
And that doesn't just apply to visible light, but also to the UVB. That black mesh has been known to shield quite a lot of UVB light from the inside of the cage: quite a few keepers using Reptariums also use 10.0 lights instead of the usual 5.0 bulbs.
As for using regular light bulbs, I have at least four 18W/20W compact flourescent bulbs (the ones sold as 'energy saving' bulbs) on top of each of my cages in addition to the UVB and heating bulbs. I am not using a Reptarium or dark mesh, but I still use the extra bulbs to get more light into the cage for the live plants that are inside the enclosure. The compact flourescents put out a lot of visible light, but don't affect the temperature gradient significantly. I like to mix up the 'Cool White' and 'Warm White' lights to give a fuller spectrum of light for the plants.