Big Lee’s Miniature Adventures has an illustrated tutorial on making model 15mm vegetable fields from corded dormats.
15mm
Gut Check Solo 15mm Science Fiction Rules v1.7
Gut Check is a set of free wargames rules for 15mm science fiction battles. What makes it unique, I think, is that it’s designed from the start for solo play. The author lists its features:
Designed from the ground up for solo play
Fast playing and zero bookkeeping
Uses normal 6 sided dice (Usually rolled no more than 2 at a time)
Uses activation rolls modified by battlefield conditions for turn sequence
Seamless Over watch and suppression effects built into system
Use any miniatures
Played on a Hex grid for convenience, but could be played with little fuss on a standard table
Three Plains 15mm Fantasy Wargaming
Three Plains is a free fantasy wargaming system. It also comes with free print-and-play figures.
Tudor House Paper Model
This full color model of a Tudor style house probably is best for 10mm or 15mm figures, but since it’s in a jpg format, it would be simple to resize it.
Stormed At With Shot and Shell Crimean War Miniatures Rules
Stormed At With Shot and Shell is a set of free miniatures rules for playing games set in the Crimean War. They’re designed for 15mm figures.