This is a quick note - we finished out the Reth campaign Sunday, and I had a few things I wanted to do with the end of the campaign. I wanted to reward players for playing without making it monetary or "best" or a competition. I also wanted to make the Apocalypse game a little more interesting.
What I ended up doing was asking my wife to help me out with a little hobby craft project. We made Reth Purity Seals (with pinback) for each player that they can keep and throw on their bag. They were cheap and quick and the players really seemed to like them!
The other thing I did to make Apocalypse a little more interesting was to create mission cards, similar to ideas I've read in the Imperial Armour books. I have no idea if they're balanced, or FAIR, or whatever, but I thought they'd be fun. I asked each commander to hand one to each player based on how they thought their force would do using that mission goal.
The mission goals were intentionally devised to have each player do something different; I don't imagine a large combined-arms force in 40k to intermix all their troops together - they'd have different objectives. In all I'd guess about 50% of the players scored their objectives. Here are the cards: