I'm trying to refine my printer ICC profile. Before I can do this I need to upload an image into the Colormunki software, which only accepts .tiff/.jpg.
I haven't used the Colormunki software, but what I assume you're trying to do is use a function where you use a representative photo of your type of work to refine the profile, yes ?
Why bother with trying to build the image from a synthetic patch set ? Why not just paint the colours you think are important onto a blank canvas in PS, save as a tiff and you're done?