Analog film photography and cameras

These are not very sharp, any ideas how to improve the results with a pinhole?

I have made rather big pinhole cameras out of shoe-boxes (exposing paper) as well as tiny ones out of matchboxes (exposing film).
Of course the "negatives" from the shoe boxes were huge but I've always found I get sharper results with bigger boxes.
I also tried, like you, making a lenscap-pinhole (but with DSLRs) - never turned out well.

The only tip I can give you regarding the pinhole itself is that I had best results with pieces of red bull type cans, making a bump (not a hole) in it with a needle, then sanding the bump with fine sandpaper in circles until you "open" the bump. Check for burrs with a loupe.

Good luck!

Ps: If you haven't yet go build a shoebox-one! It's big fun!