Long ago, I did some conversion work to this thing, and quite a bit of what I did now involved repairing my earlier, slightly cack-handed efforts. I ended up building a havoc missile launcher out of plasticard and old tank parts, and adding some sandbags to the top, which came off an old Italieri model house (of which more later, when I get round to it). They're not strictly in the right position, but this is 40k, where nothing makes much sense, and they fitted so well that they had to go on.
I painted it to fit in (roughly) with my chaos marines. Rhinos are always rather boring, and I'm not that keen on the highly-converted sorts that a lot of chaos armies use, with fangs, piles of skulls and dribbly Nurgle bits (each to their own, though - I've seen some excellent conversions like that). So I went for a battered, brutal look, as if it's been around the block as well as in Hell. Overall, I think it probably is a bit low-key, but I didn't want to overwhelm it. Anyhow, it looks like this:
Of course, Rhinos have always been too small, and I doubt a modern chaos marine could fit into this thing even if he took the horns off his helmet. My solution is that either the Rhino contains a warp portal that makes the troops magically appear within three inches of it, or that they use the magnetic soles of their space-boots to stick to all that extra armour as it zips them across the battlefield.