This street artist(s) is probably the most popular in the u. k. today, and is known for his/her witty spray paint and stenciled works:

I believe the artist that you are trying to describe is Banksy, he/she is an anonymous England-based graffiti artist.

your word would be isle.

isle is an island or peninsula especially a small one.

if you add the letter "a" you get aisle, which is a passage between 2 rows of something like chairs, shelves, or something else.