Here is a vector of abstract colorful background from backgroundvector.com. This image is a vector illustration and can be scaled to any size without loss of resolution. This image will download as a .eps file. You will need a vector editor to use this file (such as Adobe Illustrator).

Name: Abstract Colorful Background Vector Image
Homepage: Background Vector
License: Creative Commons Attribution 3.0
File Type: EPS
This image is a scalable vector graphic and can be scaled to any size without loss of resolution. This image will download as a .eps or ai file. You will need a vector editor to use this file (such as Adobe Illustrator or CorelDRAW).