I have the same problem and eventually managed to resolve it. Have to say that this is exceptionally annoying.
I ultimately fixed this by updating the Mac contact for myself. Because I couldn't simply upload a picture (more detail below), I did this by copying the picture to the \Library\User pictures\Fun folder, then editing the contact in the Contacts app (where my picture was now available to select under "Default").
That's the solution, now for my rant (and hopefully at least some useful background info):
Firstly, the image does not come from the gmail contact, it comes from the gmail "My picture" setting. If you go into settings in gmail the incorrect picture is shown there as well. It might well originate from the Mac contact, but in gmail it does NOT come from the contact, so updating the contact in gmail will not change it.
Secondly, switching off contact sync to solve this is really not a solution. If you have hundreds of contacts that you would like to keep in sync then it doesn't make sense to switch it off just because Apple has introduced some rogue behaviour that updates a gmail setting from one contact instead of just syncing the contacts like it was supposed to.
Thirdly, when I do go to my own contact in Gmail, the image is not the incorrect Apple one, it's my image that I want to use. So it seems that the contact sync, instead of syncing the contact image to the contact (which would make some sense) actually does not do that and instead it updates the Gmail picture setting. I'm not 100% sure it is the contact sync that's to blame though. From various google forums posts a lot of users reported similar behaviour with chat clients (esp. Pidgin) updating the gmail pic, so I suspect Jabber in my case is to blame and not the contact sync.
To make matters worse the Apple contact picture options are really limited. I.e. I cannot simply upload a photo. It has to come from iCloud, or from Camera, or from Photos. Since I don't use the default Mac photos app and do not store my photos on iCloud I cannot upload the right picture and had to resort to copying the file to the app's library folder as described above.
Not sure if this is an Apple issue with contact sync or Jabber or a Google issue (Gmail should not allow these apps to change the settings surely!), but it is very annoying.