Hi Jens,
been studying the picture, even downloaded it....rotated it 90 degrees at a time......unfortunately I see fighting men....then again a rider and horse (reared up on its hind legs) ...etc. Its a bit like looking at the clouds and making shapes and images from them...
Could you try and post a few more pics.... it could make a difference. Have you 'cleaned out' the stamped area ? could provide a better image if you did, it certainly made a massive difference when I cleaned out the 'Katar' mark on my Tulwar.