It would look good actually made out of walnut. but staining pine never goes as well as you think it will...and the pine IKEA uses tends to be fairly knotty (although this bed seems to use slightly higher grade wood than the next cheapest raw pine bed). Also...the general finish isn't great so you can't escape some sanding (stain will just raise the grain and make the finish imperfections noticeable).
I've had some good luck with black walnut Watco Danish Oil on pine...but the process to get a good finish is pretty laborious. Sand smooth, flood with oil and keep wet for a while, then rub off excess with a rag and let dry (and rub off any seepage a few times while it is drying). Come back and repeat, but apply oil by wetsanding it in and creating a slurry which helps fill holes and grain, then remove excess and dry. Repeat that at least once more and you should have a pretty awesome finish. Some day maybe I will get some good pictures of the pine I have finished this way. Unlike stain, it actually takes the color in a decent way (also looks good un-colored). Comes out with a little more contrast in the grain than some other woods, but it feels great.
This is what ordinary stain looks like on ikea pine (and it looks like they still did a bunch of sanding):
Warning: Spoiler! (Click to show)
That's a good example of it, and even then it is pretty splotchy.