Yeah, Xsi Mod tool is great for beginners, because its free and also because it has all the features you need at first. After all, its not like you're goint to be messing around with animation, compositing and GI renders...
Gamerking, I don't really like the Nautilus concept (I know you didn't draw it, just saying)... the shell makes it look too much like a snail, despite the tentacles. A squid is still at the top of the list as it combines the alien look with a predatory feel. But I'm still open to suggestions!
Admiral_Kiernyc, Xin explosions are going to be different, yes. I don't know if there is going to be any crystallized water in them as the ships explode in a superheated ball of blue-hot plasma, so I assume any water in it would be instantly evaporated. The current drone explosion has sort of very complex light glowing threads expanding and fading rapidly in the aftermath of the initial blast. Though I expect I'll make it look much better for release. If you like my Volumetric Explosions mini-mod, you shouldn't be dissapointed.