I recently found out that the maximum memory limit for Session Graphics in Citrix XenApp 5 on Windows Server 2003 can be increased above the 8 MB limit that is seen in the Delivery Services Console. Here is a link to the Citrix document explaining how to increase the limit: http://support.citrix.com/article/CTX114497
Basically, all you need to do is change the value "MaxLVBMem" located at "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\Wds\icawd\thin16" to a higher number. I used the decimal value of 16777216 and this allowed 16-bit color for applications at much higher screen resolutions than before.
After making the change, you must also change the permissions on the "thin16" key to deny "set value" access to the SYSTEM account. This prevents the SYSTEM account from changing the value back to a lower limit.
