Cool. I like doing conversions too and creating my own models. I've done that with my fantasy army (Chaos). For example, instead of just buying the giant, I wanted a giant snake (because I have a slaaneshi army and a snake fits perfectly into that). So, I made the entire thing with epoxy putty.
Its actually almost done right now. All I have to do is finish up it's scales, then primer and paint it. Its not right to call it a conversion, since I made it completely from epoxy, but I'm hoping that maybe I can enter it in a contest at my GW store, or something. They may not accept it though if they don't feel I used enough bitz or GW pieces to create it (I only used the end of the tail and the horns from the Galrauch dragon model).
Anyways, you should consider drawing some more Warhammer stuff. I've been wanting to myself.