I've used journal boxes for photo mats and vice versa. I'm always wary about over-embellishing colour kits because I don't know what else is going to be on the page (so i don't want to make it too girly or otherwise unusable, or clash with stickers). I sort of feel if I send them "clean" then the user can play with them to suit. I like them embellished, don't get me wrong, but I have had problems with where to use them sometimes, or the embelishment takes up some of the space. Having said that you've never seen me pass them forward
I like one photo mat, as I generally only have one full-size matted photo, or one "main" photo. I find on a single page two photo mats plus other elements is a bit too much, so I end up stretching over two and then having to find something else to fill the gap - yes, this is good, or I can split the kit, but if I only have 3 pics its another decision and I'm not good at them

Also (selfishly) two photomats is a lot of cardstock, and if its a biggish group I often don't have enough of the same colours for everyone (because I tend to buy my cardstocks in mixed packs as I don't have a physical store to get it from). Six can be a stretch for me.
I hear the point about mixed colours - how about a group of "shades of", a group of "combos" (e.g. blue and yellow, orange and brown or whatever the maker fancies) and a mixed group?
OK, nuff talking from me
