Hi i found a solution:
I Added images for "dir:" in /etc/pve/storage.cfg
dir: local
path /var/lib/vz
content iso,vztmpl,backup, images
lvmthin: local-lvm
thinpool data
vgname pve
content rootdir,images
On my older proxmox there was no setting for dir: at all, only for lvmthin: local-lvm
Problem solved!
Thanx for the hint