program that stitches together a bunch of image files into one giant poster?

[Petr]

Interesting idea. Look here https://qb64phoenix.com/forum/showthread.php?tid=3086, from the last source code select SUB LoadFiles and all the necessary SUB, Declare Library and Functions that DirEntry.h needs (it's in the ZIP file). LoadFiles takes all images from a folder and tests them for validity and usability in QB64. The rest of what you describe, you really have plenty of room for imagination and for various effects. Use the _Width and _Height functions to find out the dimensions of images, the latest IDE has the SaveImage function to save them in many formats. Also look at the _File$ function, you might be able to use that to search for images on disk.

For image rotation find RotoImage in the forum.