If you don't have the Trapcode filters, several built-in AE filters let you do custom particles based on other layers in your comp, if you consider Foam, Radio Waves, and the like particle generators. The Genesis Project shares a CC Particle World example project and gives you the project. Particle World and CC Particle Systems II are both way faster than Particle Playground (there are several Creative Cow tutorials for PP), but it's still faster to pre-render the custom layer down to near the size of the particles.
In a simpler project, Jim Tierney shows you how to Create Confetti in After Effects 6.5 with AE’s CC Particle World Plug-in. Cycore has since improved many of the controls in the newer version, CycoreFX HD.
Update: see the tag particles and check for some of the many Particle World tutorials by Andrew Kramer.