Headers or attached files in templates have size and format limitations, which vary depending on the type of file (image, video, PDF, etc.).
Text:
Maximum 1024 characters.
Image:
Only one image allowed, either .PNG or .JPEG, with a maximum size of 5 MB.
Document:
Only one document allowed, in .PDF format, with a maximum size of 64 MB.
Video:
Only one video allowed, in .MP4 format, with a maximum size of 16 MB.