These are the standard Facebook Image Dimensions.
Lucinde Grande (Mac) / Tahoma (PC)
Facebook Cover: 851px by 315px
Partially covered by Profile Picture and by Sign Up / Login when a visitor isnt logged in.
Facebook Profile: 180px by 180px
This shrinks to 160 x 160 on the page
Facebook Tabs: 111px by 74px
The photo tab cannot be moved but will change when uploading images