How to made collage frame for large wall?

Use an old picture you get from the St. Vincent DePaul type of thrift store and attach you items overtop. Paint the frame to match you decor.

How To Make A Picture Frame Wall Collage

https://www.elevenobjects.com/how-to-make-a-picture-frame-wall-collage/

Here is another idea for you

https://www.youtube.com/watch?v=ans3F_8Lg4s

Here is an idea using a window!! I love this idea and you can do it vintage looking(chippy paint) or NOT.

https://www.hometalk.com/diy/decorate/walls/window-pane-door-turned-picture-frame-31096401

Lis: maybe this will help

https://www.diys.com/photo-collage-ideas/

Hello. Not sure of your aesthetic but if you want a collage frame for photographs or cut outs perhaps putting up cork tiles framed by molding might be an idea.

The cork tiles mounted on a thin piece of Louan or MDF might be an option with a custom frame built around it

Here's some creative ideas from Pinterest;

https://www.pinterest.com/milanmom02/large-collage-picture-frames/

Here's another idea for you: https://www.youtube.com/watch?v=U9EEmKlTfW0