Okay, first the good news:
I have completed the fourth set of my nebula backgrounds.
Now... the bad ones.
When putting everything together I ran into several things that shouldn't be happening:
(1) Although I had been told the limit in stars.tbl had been bumped to ~150, I found out that FRED2open will still only show as much background images as were permitted in standard FS2.
"Well," I thought "they prolly only forgot to compile that into FRED, i'll just use NotePad to do the job..."
(2) Now, I had re-included the standard FS2 backgrounds. I started the game only to find out that if any background image that will not show up in FRED is used, the game will crash after loading the mission. Now, I thought the bumping just wouldnt have been done, but I found out later, that the game will display any of the first background images (the ones that still show up in FRED) okay, and only crashes on those that come after the stars.tbl limit (which is still the same as in FSretail). Older builds simply do not show up ANY background images, if the stars.tbl limit is exceeded. So - the bumping has been (at least partially) done, but doesn't work.
(3) So, I tossed out all my other sets to at least test it in-game once. I then discovered that the lighting in the new build (with diffuse in again) is indeed odd, as the actual background nebula images are rendered too bright and look a bit odd - as well as the ships (see my post in the recent builds forum). I think the problem is that 'diffuse light' and ambient light add together, and so the general light factor is way too strong. The solution probably would be to get rid of diffuse lighting again, and have ambient as the replacement (as it will look better with in-game effects (sun lighting, beam hits, etc) ).
(4) Then, I wanted to test with the new env_2 build, to get some nice screenies even *with* the odd brightness, but when I hit the run button on the launcher, FS2open immediately dumped me back to desktop with an illegal operation. (before even opening it's screen) So ~ as a summary of the day:
- The limit in stars.tbl needs fixing, so we need a new version of FRED as well as FS2 that will handle the new limit okay.
- Something has to be done with the lighting
And to encourage you to fix things:

(I know it's a bad screenie, but I was too frustrated to come up with anything better)