CGI for a logo would probably be fine if it's fairly small and non-impressive (a basic text logo or something), but if it's noticeable enough to get your save extra votes, the save will probably be locked until you remove it. In my opinion, cgi really isn't worth it unless it's something you know is acceptable.
My general test for saves that break a rule is:
If the save in question does answer yes to any of these questions then it is likely to be removed. As with what
@FeynmanLogomaker said, in my opinion and stance for CGI, if it isn't major (logos or something small) then I won't stick you for it. If you use it to make a major art save or electronics system for votes and attention, then that would be an unfair advantage.