Dave provides the following:
'Joseph Trensentsky was a lithographer and according to this: http://www.weber-gesamtausgabe.de/en/A005503 he set up a printing company with his brother in 1819. There are a lot of lithographs from the 1820s and 1830s he published, which show battle scenes, but with the later uniforms. Also, the uniforms are still roughly Napoleonic right into the 1850s, so these lithographs tend to be misdated back to Napoleonic times. You can however see that the trouser knots become steadily more elaborate and the shakos develop the later bell-shape.
Like Hans-Karl, I noticed the Stabsdragoner background is copied from a plate by Klein dating from 1814-16. From other pics like this http://www.artnet.com/artists/heinrich-papin/k-k-oesterreichische-landwehr-ojh3NecMEtZmWJVagHxNoQ2 they seem to be early 1820s, Papin himself dating from 1786 to 1839. In the second lot, the Hungarian Guard cavalryman is 1823, painted by Franz von Hauslab and printed by Trentsensky. That comes from a set Hauslab painted, several of which are shown in Allmayer-Beck 'Das Heer unter dem Doppeladler' Vienna (1981). The second one, being a coloured version of the Stabsdragoner, comes from the Austrian National Library's Bildarchiv of pictures and they are gradually putting their collection on line. One plate they have shows the metal decoration, representing short feathers, which is visible on the shako of the Hungarian Guard cavalryman.
The last one is from the 1810 Eder drawings, which are rather idealistic, but interesting anyway."
A Big Thank You to Dave Hollins. <;^}