I just checked the fifth image from the top (the kitchen)
http://si.wsj.net/public/resources/images/OB-UG852_IKEAb0_G_...
in the real catalog. I would never have guessed it was not real when browsing through it. If I knew there were some it could have been a candidate because there are no people in it. But otherwise, it looks like a very regular photograph.
EDIT: Mistake! I did not look at the correct image, mine was similar but different. Disregard the above.
EDIT 2: So this means I am looking at a picture in the catalog that I don't know whether it is real or rendered. But knowing that they new render some images, that the image has no people in it (which is not uncommon in the catalog), and that especially the cupboard doors have some artificial feeling to them, my guess is that "my" image is rendered too. But also, there is a bottle of olive oil on the counter, and its brand is a brand that is common in Sweden, and contains details on the label that seems authentic. So they put much effort into small details in that case.
EDIT: Mistake! I did not look at the correct image, mine was similar but different. Disregard the above.
EDIT 2: So this means I am looking at a picture in the catalog that I don't know whether it is real or rendered. But knowing that they new render some images, that the image has no people in it (which is not uncommon in the catalog), and that especially the cupboard doors have some artificial feeling to them, my guess is that "my" image is rendered too. But also, there is a bottle of olive oil on the counter, and its brand is a brand that is common in Sweden, and contains details on the label that seems authentic. So they put much effort into small details in that case.