I don't decorate my album covers either.
For journaling, at a minimum you should include the names of the people in the photos and the dates (even approximate dates if you aren't sure) of the photos. Just jot this down somewhere on the layout or even on the back, then you (or others) won't be looking at the album in thirty or forty years and wondering, "who ARE these people anyway?" After that, it's totally up to you.
Scrapbook sketches (like the ones at PageMaps - google it) usually show an area of the layout where journaling can go. Look at the sample layouts at PageMaps or in the gallery here for ideas on all the different techniques you can use for your journaling.