I just received my order for bookmarks and am quite happy with it. This bookmark was printed on a postcard format twice. That is, I placed 2 of these, side by side, and used VistaPrint postcard services. I only needed a few, so I'll take the postcard doubles to a local printer, who will slice them in two.
I only needed a few, because I'm doing a program that explains the different subgenres of romance as it is today. I speak Sunday, Oct 4 at noon at the Missouri Literary Festival.
To create the first bookmark/format, use a graphic program. You'll need measurements to match the printers specs for a postcard. Lay out a background and then add new layers for each cover/photo. That way, they are moveable/adjustable, until you flatten.
I usually leave the original unflattened. That way, if I want to make changes later, I just assign a new name for the update and flatten that one. The backside has two parts to match the front bookmarks. It lists my E-mail, Twitter, Website, etc.
Notice that some of my covers go right to edge of the cut. That is called full bleed. You may want full bleed, or to use the inside cutting margin and draw a rectangle inside to create a border.
This pattern was used first as a .jpg for my Twitter page. But I changed the dpi to 300 and it worked well for 4-color printing. Not advised though.
I wasn't quite certain how these would turn out. But I'm happy with them.