That's quite an impressive piece. The whole thing is paper, and you haven't reinforced it at all? The thing that my eye is immediately drawn to is the bent barrel I'm afraid. The artwork is lovely, but like other posters say, it looks painted. Well painted, and pretty, but still painted and you're probably going for engraved.
A bit of sandpaper and car bodyfiller (bondo if you're in the US, I'm not) will straighen it out nicely, given a few hours, a respirator, some vinyl gloves and a bit of experimentation to figure out how to mix the stuff properly in the first place! If you don't like the idea of bodyfiller use green stuff (epoxy ribbon is its fancy name), modellers' putty which isn't toxic. You'll find it ridiculously overpriced at Games Workshop, and can find it considerably cheaper elsewhere online.