I’m assuming you mean prints and stuff.
Jealous are pretty good. Have shops in Crouch End and Shoreditch.
https://www.jealousgallery.com/
Print Club used to sell stuff from their place in Dalston, not sure if they still do. Can often get some real bargains there. Got a Ben Eine print for £35 a few years back.
https://printclublondon.com/shop/
Stolen Space on Brick Lane has some nice stuff
Nelly Duff, but not been in years.
https://www.nellyduff.com/
Half the things I buy are sat under a bed never to be framed.