Borders and photo mats/frames do not have to be identical. Most swappers will coordinate colors. If you check out some of the links to previous swap posts--see swap calendar sticky--you will see what I mean.
Sometimes people will do the mats or frames in reverse: for example, red on top, black underneath on one, then black on top, red underneath on the other. Or they will use three or four colors. In the past swaps not all frames have been double matted. It depends on the frame's style, embellishments, etc. check out the link below to see what I mean.
disneylandemily has a lot of the photos of past swaps at this link--these will give you great ideas! Swaps are numbers 14 -- 24.
http://albums.photo.epson.com/j/AlbumList?u=4084831
Someone had a question about tags--I usually use my sizzix die cut. I have some from other swaps that are 2" wide by 3 to3 1/2" tall and 2 1/2" wide by 4" tall when put together. I believe my sizzix die is a little smaller. They have come in all shapes, too. There are examples of tags in the links above, also.
I think that is all the questions, if there are more, post them and we will get them answered!