Instead of a simple journal/scrapbook cover, why not try one of these where a detailed frame has already been added with an opening for whatever you choose. The covers have two predrilled holes (8mm diameter) set 85mm apart.
This is a self assembly set of which includes 8 separate elements:
2 x pre-drilled covers (one of which has an opening) made from Birch Plywood.
Cover Dimensions: 151mmx210mmx3mm
Internal Frame Detail: 105mmx118mmx3mm
Decorative Elements: 55mmx25mmx3mm