Today Google + launched an all new looking interface. the new google + interface changes have been applied across both personal and business pages.
Google have advised they are staggering the release of the updates, and expect it to take several days to apply to all Google + profiles and pages.
I've seen all of our clients change, although some users have reported no change yet.
An interesting note, there wasn't really any notice like the recent facebook updates, maybe its just because they don't expect the Google + user backlash like facebook experienced during the timeline changes.
(PS Still looks like FB clone even more so now)
Facebook Page Image Dimensions
On with the dimensions.
Google Plus Profile Image: 250 x 250 (px)
There is also now a user choice to keep the existing 5 small square images or the new 1 piece cover image
Google Plus 1 Piece Cover Image: 940 x 180 (px)
Although only 900 of it appears (white page component overlaying the right final 40 PX)
Google Plus Multi Piece Cover Images: 110 x 110 (px)
Note: Take care when selecting the cover photo option to not weight to much content on the right side, as it will be covered by the profile image, and the 40 PX overlap as mentioned above.
There were a range of other features implemented, these include: larger images, easier navigation (left menu) and some hangout related changes.
Here's a pretty sweet video by Google showcasing the Google plus changes