While purchasing a piece of art in small increments would make collecting available to the masses, you just can't build La Parade de Cirque one point at a time, or cobble together a Picasso out of individual weird face-boobs. For wall decor you can grow slowly, hit Modular A.R.T
From a BK based designer looking to "make modern art more accessible and interesting to the average consumer", A.R.T.'s a "fully customizable modular art collection" consisting of individual units that can be purchased & arranged in any quantity, and modified as your income or domicile space increase (if the latter happens before the former, surprise, you're in Brooklyn!). Designed by a group of artists, architects, and designers, the headliners are hanging sculptures called Wall Art: interconnecting plate-sized units that come in three shapes (square, rhombus, and boomerang-ish "reticles") that're adorned with various geometric patterns, made from materials including multi-colored acrylics, felts, and woods like walnut, white oak, and American cherry, and who doesn't wish they had more of that in their life. Made-to-order using CNC machines, pieces are shipped unconnected so you can unleash your creativity and develop the form that most fits your abode; or just leech off creativity of others, via replicable pre-designed patterns worked up by the unit's artists, making for your finest act of art plagiarism since you mastered Bob Ross' trees. Guy had a sick fro, though
To accompany your new hanging sculpture, there're similarly-geometric mural's (aka blocks of wall paper) designed by the same artists, plus "shelf art" consisting of blank books with spines in a range of tasteful colors, because building a library in small increments is good, but only if you don't have to actually read.