It doesn't look like it's possible to do it that way. After a bit of google, it appears that both the -e and -x options are designed to mimic the -e option of xterm, which is to simply launch a command and then exit.
The only easy solution I can think of is to add your command to the end of bashrc (or the config script of whatever shell you use), then it will run during initial start-up.
I'm not sure about the best way to limit it to gnome-terminal only though, if that's what you want. A quick test shows that it sets the COLORTERM variable, however, so you should be able to use that.
if [[ $COLORTERM = gnome-terminal ]]; then