Dear @Mateusz, 

Thank you for highlighting this; the shop is X20, a series of currently 29 shops specializing in everything for bathrooms - as in 'taking a bath', not a 'going to the toilet' kind of bathroom. 

Their page is at https://www.x2o.be/nl/showrooms/x2o-badkamers-st-niklaas ; 

As an aside: in Flanders we tend to assign different meanings to common words : 'hangar' is any large storage facility - for example the open sided shed roofs along the quay side in the 19th C.  port, or a modern logistics centre; 

shops specializing in bathrooms are called 'sanitair' - on occasion these recycled words are a source of amazement at the ingenuity; 

To translate : the shop next to it, Gamma, is part of a general hardware / building supplies chain, while X2O are at the higher end of the market. 

So how to tag? To the north-east you'll see Aveve : they're not just a garden centre, also sell pet and animal supplies, home baking and jam making - they're originally part of the Farmers' Union, some of their establishments have several tall cattle/ poultry feed silos, others look like any retail park 'tin shed'. 

And Gamma isn't just DIY, during office hours you'll spot local builders firms buying their supplies. 

Plumbing, then? Well, that'd be the bloke who de-clogs your toilet or mends your burst pipe. 

What about https://wiki.openstreetmap.org/wiki/Tag:shop%3Dbathroom_furnishing ? 

Met -als immer- vriendelijke groet (Dutch for 'with -as ever- friendly greeting'),