Hotel suggestions close to the conference venue:

Elite Hotel Carolina Tower (~10 min walk to the venue)
Blique by Nobis (~15 min walk)
Elite Palace Hotel, Stockholm (~20 min walk or short bus ride)
Best Western Time Hotel (~20 min walk)
Giò (~20 min by public transport / ~30 min walk)
ibis Styles Stockholm Odenplan (~20 min by public transport)
Best Western Plus Park City Solna (~25min by metro/bus)