Go on. This thread started with someone wanting to display a bitmap on his 128x160 TFT. It was solved by #2.
Yes, ideally his project could be organised as project.ino, bitmaps.h bitmaps.c
bitmaps.h could ensure correct types and linkage
The OP started with PNG and used a PC tool to create the appropriate C array. I do not know which tool.
I would be interested to know whether your application is able to perform this common task.
You do not have to tell me. You can keep it a secret.
David.
Edit. My apologies. It looks as if you can "import" a graphic and "convert" it to a C file according to a "image.tmpl"
So it is possible to create C files with suitable format for Arduino projects. C files from your default template do not compile.