I doubt they haven't made advances in light bulbs in the 23rd century, maybe to the point where tiny dots can produce large areas of illumination on a starship by some wondrous means of treknobabble. Or some hidden focussed lighting system inside the lower sensor dome that casts light on just that area, or any other kind of fancy futuristic explanation a person can think up. Not everything on a ship has to be totally realistic, especially considering that our idea of real doesn't take into account 300 years of development.
I also never said the blue area on the Bellicose was the same as the one on the Excelsior - they just both have a similar appearance. I intentionally leave some parts of a model undefined so people can come up with their own ideas to explain/expand them. Besides, it just looks cool to have some fancy blue light back there to liven up the ship's 'ooo, ahhh' factor a bit.
Nice work on the retextures, WD. I noticed the hull registries are improved (I forgot to fix that on my last release), namely the red outline. Incidentally, I should point out that the lower hull details (the circle and boxes behind the phasers) weren't added to the Enterprise until the E-A. The TMP version only had the phaser banks while the rest of it was blank. They obviously added the details to spruce up that part of the ship and slip in a reference to the TOS version. Most just assume it was always like that since they hardly ever show that part of the ship. There was a blank and E-A version included in my last release of the Connie, along with a few other minor adjustments. Of course, my site's offline so the point is kinda moot.