I've soap finished both Ash and Oak. It's about as fashionable as you can get at the moment, matt but with just a hint of burnishing on the arrises, like bone or driftwood. Ideal for a picture frame as long as it's well made...there's a lot of water involved in this! The FW article covers it off pretty well, not much reading up to do, it really is dead simple. Don't over complicate it, just do the simple basic job and leave it at that.
Another similar and very fashionable finish right now is to use a two part bleach on Oak, and then scrub it with a mild abrasive like Vim or Ajax. You rub through the bleach on the edges and corners and start to bring back some of the pale Oak colour.
Those two finishes, together with scorched/textured Oak and an iron stain, are pretty much where most of the big name designer/makers are at the moment.