Veerle's Blog has background on CS5 icons and splash screens in The new CS5 branding (via @simoncolijn). See the new ones for After Effects; there's a variant from the designer on Adobe Inspire.
Adobe’s Desktop Brand team says they drew inspiration from a wide range of sources, including traditional drawing tools, machined metal surfaces, Swiss design, lithographic advertising posters of the early 1900s, and more. In particular they found inspiration in the work of Otl Aicher for the 1972 Munich Olympics, which used an isometric grid system.
For related background see Heller’s animated appraisal of Olympic pictograms.
Update: on the Adobe blog Typblography, Miguel Sousa discusses Fonts for the CS5 file type icons.