That's my story and I'm sticking to it!
If you haven't signed up for Fat Dragon Games' newsletter you need to do so like yesterday (from Facebook, links are mine):
"PLEASE READ! Starting later this month, FREE expansion tiles for the 'DRAGONLOCK Lost Dungeons' set will be included in at least one Fat Dragon Games newsletter each month for the next year (we usually send 2-3 newsletters a month, and at least one of them will have free expansion models.) The models will not be available to download indefinitely, so make sure you watch for our newsletters! You can sign up for the FDG newsletter on our website under the 'Resources' menu."
These will be limited-time freebie offers for expansion files that will eventually go up for sale. Jump on this opportunity while you can.....
....come on, you know you want to!