File Juicer
File Juicer for macOS
Overview of Formats

Search & Extract

Images

jpg jpeg 2000 gif png pdf wmf emf tiff eps pict bmp

Video

mov mpeg avi wmv

Sound

mp3 wav System 7 au aiff

Text

ascii rtf html

From:

avi cab cache chm dmg doc emlx exe ithmb m4p mht mp3 pdf pps ppt raw swf wps xls zip and other formats

.thm - Canon thumbnail images

A simple way to view these files is to drop them on File Juicer and let it extract the JEPG inside. The files are typically tiny - just thumbnils to show on the built in display on the camera. There is nothing more than the JEPG inside and you can also just rename them to JPG if you just want to look at one of them.

File Jucier can also find thumbnail images inside Canon's more advanced CR2 and CRW files.

.thm - Sony Theme Creator Files

You can decompress these files by renaming them to .tar and double clicking them in Finder.

Sony Theme Creator has been available for macOS, and maybe you can still find it