[Ok, this doesn't make sense now as I changed it!]
I think I'm going to leave it there as a good example of why you should NOT set up custom sizes for things in MyMemories. I set this one up at 800 pixels for the Facebook group header and it was too small for Blogger. Adding it to a plain background of the same colour in a new page didn't work. It's driven me barmy.
The best thing to do - always and despite what a gaggle of bossyboots will tell you - is to make a regular layout and resize it once it's finished in the very handy Picmonkey or any other program. Now I'll have to start again or - even better - get the designer in our team to design it!
The header for the Facebook group is about to change, leaving out the .com. Why? Because the dot com will shortly be going to ...a new website. watch this space. Just try not to look at the header.