The New York Public Library’s Digital Gallery has a large collection of prints of Austrian uniforms from 1448 – 1896. It’s an incredible painting guide.
Chronofus has written a wargamers’ guide to Napoleonic Austria. He writes:
This document is a wargamer’s guide to Austria in the disastrous campaign against France in 1805, written to suit the Elan rules system. This is not intended to be an in depth detailed study of the campaign, which must be left to Europeans with good access to archival material. Enough information is presented here to give an overview of the campaign itself and enough formation and uniform details for a wargamer to suitably paint and base their miniatures to a reasonable standard. There are enough vagaries in some units for perfectionists to require further details from more in depth historical analysis. The reader is also cautioned that there has been, and continues to be, alot of misinformation about the Austrian army. Many parts of this campaign where Napoleon was not present have also been conveniently buried in history. As far as practical this document has been verified against current research.
I know you won’t believe me, but there’s more to painting Austrian Napoleonic uniforms than endless seas of white. You can find more details in the uniform guide here.