[Akalabeth Angel]

Hi, I'm building a campaign right now and a lot of the early missions are set within a system with a nebula backdrop. One of the missions takes place within an asteroid belt within said system, so I decided to use the asteroid.pcx from Inferno because I thought they were pretty good. The first time around it, the asteroids had big blocks of black around them. So I loaded the .pcx up PSP, increased colour depth, changed the black to 0,255,0 (transparent colour?), decreased colour depth to 256 and then saved it.
  Now when I try the mission again, the asteroids don't show up at all. Even though they still show up in Fred. What's the deal?

If it matters I've got the backgrounds appearing in this order within the .fs2 file. (I've also got an actual asteroid field as well)

Sun
All Nebulas
All Asteroids

    Basically what I want is the the sun and the nebula in the background, and then the asteroid bitmap overlapping the nebula where appropriate, and then the actual asteroid field ontop of that.

[CP5670]

I did this a few of my missions as well. Your ordering of the backgrounds looks correct so it might be a problem with the asteroid file you are using.

There a set of standalone asteroid backgrounds (made by Ice Heart, I think) floating around that work pretty well for this sort of thing; see if you can get hold of those.