Vinyl wall decals are still flooding the interiors market in bright new forms, like these examples from Etsy shop Empire City Studios
, so liven up plain walls with a decal or two, or three! You can keep your selection abstract by choosing something like the circular spirograph patterns for a quicker and cheaper personality injection than wallpaper, or try a cubist arrangement for a budget splash of modern art. For more specific zoning, you could add an air of café cool over your dining table or breakfast bar with a hot coffee cup symbol, it's a great way to add a quick burst of character to a boring corner.
Grander pieces of vinyl wall art such as trees look great in just about any room, imagine a delicate spray of branch blossom blowing over a crib, or a graceful bough swaying over your sofa; add a flock of colorful birds to your branches and you can span your room with an impressive feature. Try to choose decals that completely contrast with your paint color for maximum impact in large areas.