I could fix the not showing graphics during the PIN query by skipping the customizing process of the original T-Mobile ROM.
In addition I found out that old installed programs are still there, e.g. Total Commander. Other programs shipped with the original ROM are missing, but icon still there, e.g. "Sprachwahl" or "ClearVue PDF".
By the way, when I tried to flash the new rom the standard way by just using the batch file, the installation process failed. Because of this I copied the files "EnableRapi.cab", "Cert_SPCS.cab" & "ItsUtils.dll". Installed the cabs & moved the DLL to the windows drive. After this I could flash the ROM.
I had similar or same error messages with the "Diamond ROM" or the "Charmer TouchFLO WM6 German Version 3.2 - by Ridingshark ".
Does this helps?