I've been collecting Heroscape board game box sets, because I flock and paint up the plastic hexagon tiles, to make terrain for games such as Battletech. However, I realised that the monsters in the boxes I got in the mail recently, look kind of like tyranids and tyranid hybrids. I'll have to paint them up in my tyranid pait scheme, but there's dog-monster aliens, that could go well as melee runners like the hormagaunts, and there's human/alien creatures with guns, that could work as armed genestealer hybrids using the hybrid rules of 2nd edition space hulk. The neat thing is, I now have 12 of each - so 24 figures I could add to my space hulk game, and add visual variation to the game.
My idea for playing at the moment, is that there are melee and ranged aliens - all melee aliens just use the genestealer rules from space hulk, and all ranged aliens just use the armed alien hybrid stats from space hulk. So, different models are just for visual interest, while keeping the actual playing of the game simple. I'm using un-armed gargoyles as flying melee units - stabbing at people with spiked tail, of close-range acid spit, etc. So, now I should have gargoyles, hormagaunts, and dogaliens, that I can use as melee 'genestealer stat' monsters :)
I'm using imperial guard stormtroopers for the human team. Their flamer is a stand-in for a terminator with a heavy flamer, and their meltagun is a stand-in for a terminator with an autocannon. The sergeant with power sword and gun is the marine with power sword and bolter, and the other guys are just treated as marines with power fists and bolters. So, I'm using the space hulk stats and rules, but using my own figures.
On another note, my brother collects space wolves, and is putting together a bunch of terminators, so we should be able to play the actual space hulk game proper at some stage :) If you haven't checked out his blog before, you can find it here: http://simbattleboard.blogspot.com/ Tons of stuff on there, including one of the Games Workshop Realm of Battle boards and lots of battle reports!
colony on an infested world
and some actual tyranids