GD was enabled on Stoli last time I checked. There may be some issues still with the PHP level system, though I am not aware of any.
You can check this yourself by using the phpinfo() function:
Make sure you delete this file or make it so it cannot be accessed by anyone who doesn't have permission as this is a big security risk.
All the modules are displayed in the function output. Just do a ctrl-F and find GD.
This is from Stoli:
gd
GD Support enabled
GD Version bundled (2.0.34 compatible)
FreeType Support enabled
FreeType Linkage with freetype
FreeType Version 2.2.1
GIF Read Support enabled
GIF Create Support enabled
JPG Support enabled
PNG Support enabled
WBMP Support enabled
XPM Support enabled
XBM Support enabled