I think that means you are using the wrong image type. I googled your error and got the following:
Go to your LogonStudio\"Name of the logon that cause problems" directory and open the Theme.ini with notepad.
Count from the top 14 lines (don't count the lines in brackets). It will say something like:
ScrollButtonUp=Bitmap_110.bmp
Note that the Bitmap number might vary, depending on the logon you use.
Then check whether you have a .bmp of the same name in this same
folder. If no, try and copy the bitmap from another logon to this
folder. If yes, the bitmap might have become corrupted and can't be
used. Do the same (copy it from another logon)
Also
Do you run an English
Version of Windows? I have heard of other similar problems with
LogonStudio which all occured on non english system. If that is the
case, you might be able to set your default Language to English, which
should solve the problem. (but then again, you might not want to do
that).