Sorry it took me so long to get back to you. I will check out the dimensions on a Facebook cover.
Would it be easiest if I created a thread and put the pictures I think could be best used in a montage in it as attachments? I have well over 400 pictures of him and probably a few dozen which could be perfect in a tribute sig/cover.
Here's what I found for the cover:
"Cover photos are 851 pixels wide and 315 pixels tall. If you upload an image that's smaller than these dimensions, it will get stretched to this larger size. The image you upload must be at least 399 pixels wide."