I had printed license plate frames for my bikes long ago but was never quite happy with them. Typical designs attach to the front side of the plate, obscuring the corners with straps or flanges. I have also seen styles that "clip" onto the plates but I thought they might be a bit difficult to print and have fit securely. Some of the ones with larger straps or flanges may not even be legal in your state or jurisdiction because of how much of the plate they obscure. Why invite being stopped over something like that?
So I decided to create versions that mounted from the back side so that no portion of the license plate was visually obscured. And at the same time I wanted a slight "hood" just for the sake of appearance.
Included are .stp, .stl, and .igs versions of frames. One has a completely flat area below the plate and one has a pocket. You can add your own text or logos to the flat version by editing the .stp or .igs files (if your CAD system can do that), or by simply gluing something over it. The pocketed version is made to accept a 160mm (6.3") length of standard 12mm (aka: 1/2") Brother P-Touch label tape, or create and glue your own printed logo into it. Slicers such as Cura will open common graphic files, so you only need to create something with any typical "paint" program, open it and slice it.
I included my two final versions for grins so you can see what is possible.
I hope these will work for you, thanks for looking.
Note that these are designed for typical USA-standard size license plates only.