TIFF, PSD and other image file types must be converted to JPG or PNG. Files need to have any embedded color profile.
Note that for printing purposes, there is no visible difference between an uncompressed file and a JPG saved with maximum quality (10+ on Photoshop, 80+ on Lightroom)
To submit any files that are not supported by the Pikto online designer, you can select "FTP Order" for Print and Wall Displays or use one of the alternative applications for Press printed products and albums. Note that longer turnaround times will apply and that files need to be prepared to avoid any additional fees.