You have to install an X terminal on your 770. You can find it here. One big problem will be to add your own theme in the /urs/share/themes/ folder. To copy files to it, you need to be root, which isn't possible without this. If you want some sample 'real' gnome themes, you should check out http://art.gnome.org/

Damn, I hate having to flash my device to get a root account. Does anyone know why Nokia blocked that root account??