Test data sets:
A 2005 publication from J.B.Heymann, M.Chagoyen and D.M.Belnap entitled 'Common Conventions for Interchange and Archiving of Three-Dimensional Electron Microscopy Information in Structural Biology', with corrigendum, addresses the issue of conventions for exchange of cryoEM data.
A set of 3DEM Image Conventions was agreed upon at a 2005 workshop held at EBI.
The 3DEM conventions website summarizes the proposed conventions.