Hi ! I would like to play the "Battles of the Mauryan empire", but I wonder if someone has already made appropriate pictures for the indian chariot and the cataphract elephant...

Philippe
I am afraid not. I don't have those skills unfortunately.
When I playtested the scenarios I used Elephants from different armies to represent Cataphracted and non-cataphracted elephants.
As for the light chariots I used Barbarian light chariot stickers on spare blocks as I have purchased several copies of each expansion. Again you could use blocks from other armies to denote them or special unit markers. The chariots aren't so much of a problem because not many scenarios have both heavy and light chariots, so when you only have light chariots you can consider all heavies to be lights.

For example in Pataliputra the Nandans can use 3 Greek elephants and all 6 elephant units are treated as cataphracted. The Nandan player can use the 2 Carthaginian hvy chariot units and consider them light.

In Maghada the Nandan would use 2 Carthaginian elephants as cataphracted and 2 Greek as non-cataphracted. The Mauryan player would do the same with eastern and Roman elephants, and both sides would use hvy chariots for lights.

Hope this helps.
Jim

Sure, it helps. That's a simple way to manage the difference between the two types of elephants. Actually, I was also thinking of using the "special unit" stars. I can't remember if in GBOH the pictures of the units are usable for blocks. But I suppose that all pictures of these games are protected by copyrights.