SpottedKitty how does BMP fair when wanting to print?
The big problem with .bmp files is that most programs saving them can’t do it with any kind of compression. It’s a very old format — I know the spec’s been updated over the years, but most of the time when I see a .bmp it’s uncompressed (the file is HUGE!!!) and not always high quality.
Speaking as a printer, the format I most like to see is .tif since it’s easiest to save properly if you don’t really know what you’re doing. A .tif file allows compression, but watch it — the .tif standard allows for various compression types to be “bolted on”, so you can have a .tif with no compression, lossless compression, or lossy .jpg compression.
Safest for image quality is .png since it (AFAIK) only allows lossless compression. Both .tif and .png support an alpha channel, so if you want to use one in your render, either one will do.
BTW, have you talked to a printer yet about file specs and settings? There are a few things you need to know before creating your final render, and some things that can wait until just before you finish postwork and save the final file that gets sent to the printer.