I don't know if this site has been posted in the past, but I have gotten a lot of free files from here and check it regularly as they periodically add new ones. They all come in pdf format and require a little bit of work sometimes to convert them into into MTC, but I find the results are worth it.
Canon Creative Park
http://cp.c-ij.com/en/index.html
Comments
in the past they have commissioned some great papercraft artists to create files
Rob Ives's being one https://www.robives.com/
Paper Modellers I Revere Marc Hagan-Guirey ----- Yoshinobu Miyamoto ----- Peter Dahmen
Gallery ID #26944 ----- Link to My Cloud Have a Look your Welcome to Make Use of the Files