I have begun constructing some 15mm scenery objects for my first scenario, of the First Crusade: The Siege of Nicaea. The scenario is written in detail in the blog post prior to this one.
Here's a photo showing one of Nicaea's towers, beside a 28mm scale Lord of the Rings: Haradrim tower that I constructed for my fantasy skirmish games. (more on my Lord of the Rings hobbying at my other blog. (http://paulslotrminis.blogspot.com/)
The 15mm scale medieval round-tower is textured using stone work that I cut out of a photo of the walls of Jerusalem's Old City region, for added authenticity to the regions I will be Crusading in.
I made it in a graphics program, printed it out using a colour printer, and sticky taped it together.