I suppose the Ustorage disk is the disk we have access to by usb on the HMI. Can you please confirm?
Yes, it is.
I do not understand where to copy the /STONE/logo folder containing the logo.bmp file (800×480, 24 bits).
Please check the below picture.
Put the STONE/logo folder directly in the root directory of the u-disk, and put the logo image in the logo folder.