If you need a backpack for your fantasy/medieval/dark ages projects, one type that is depicted in period paintings, illustrations, and tapestries is sort of a large basket with straps. These seem to have leather or even rope straps. Some have a "lid", most don't.
I've created a Lora to help give you that "medieval feel" with this basket backpack.
The images I've used for training come from ren-faires, re-enactors, living historians etc. So MOST of the characters are wearing wool tunics, wool trousers, aprons, dresses, chaperons etc. So to use it in a modern setting, you might have to play around with the weighting.
The main trigger word is "basket-pack", and some of the image tags include:
Wearing basket-pack, dark brown basket-pack, tan basket-pack, basket-pack loose weave, rope straps, leather straps, leather trimmed basket-pack
Some of the images I used showed things inside the pack being carried... these were often "grass sod, sticks, furs, or i tagged the general "goods". You can prompt this yourself using, "basket-pack with goods" for example.
It responds pretty well to having things "put in" the basket-pack that were not in the training images... you the same trigger (basket-pack with ITEM WANTED"
Have fun with it, and post any cool images you come up with.