We can accept a few different file formats e.g. JPG (the #1 Preference), TIFF, PSD, PDF etc. BUT,

We have done many tests regarding file formats and the end results are that if you have a TIFF file say a 400MB file vs. the same file saved as a JPG at the Highest Quality Setting 40MB file and they're both printed via same Software and printer you will NOT be able to tell the difference. 

We've had clients where we have done this experiment with their file to show them and they have been unable to tell what print was JPG and what was TIFF as they looked exactly the same.

So, JPG it is! :) Smaller file size, yet great quality for Printing.

We require your files to be supplied in RGB.