Here isa vector set of 3D boxes, includes a eps file.

Name: 3D Boxes Vector Set
Homepage: EPS10
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).