I haven't tried this yet, but it seems possible. My kids have a number of little sand castle molds -- castle-shaped buckets you use at the beach to create sand castles, towers, etc. They're hard plastic and sell at Toys R Us, Wal-Mart, and other general big-box stores for about a buck each. Some are actually quite well suited to work as 40K guard towers (or for 15mm minis games), having slightly sloped sides, crenellations , and enough flat surface on top to pose a few minis. Unfortunately, they tend to be bright red, yellow, green, or blue. Now, Home Depot has a product is used like spray paint to create a faux stone or faux granite finish (it's actually a two-part process). I'm thinking that a few of those sand castle molds covered with this faux stone and - voila - quick buildings for use in your Tallarn campaign. Since those buckets aren't in stores right now, I'll have to wait until summer to try it, but I thought I'd share the thought before it scampered out of my overfull and much-abused noggin.