Ooh, ooh, let me add some. Unsurprisingly, most of the ones I recognise are from cartoons.
In the back row, I can definitely see the titular Robot Monster, as well as Torg from
Santa Claus Conquered the Martians, both of which I know from MST3K. In the same vein, Jet Jaguar is just behind C-3PO.
Weebo, the robot from
Flubber with Robin Williams, is just in front and to the left of the Robot Monster.
Now let's start from the front row and work back.
Just behind R2D2 is the titular Robotboy from his short-lived Cartoon Network series.
To Robotboy's left is XR, from the Buzz Lightyear animated series.
In front of R2 is Goddard, Jimmy Neutron's robot dog.
Just next to C-3PO is the main character from the film
Robots. Next to him (behind Bender and EVE) is Zeta, from
The Zeta Project.
A space or so down from Zeta is Plex, from
Yo Gabba Gabba.
In front of C-3PO is, I'm pretty sure, the robot butler from that
Clone High show I've never actually watched.
Moving over some, just behind Humping Robot is X-5, the robot from
Atomic Betty.
Next to Humping Robot is the titular character from
Whatever Happened to Robot Jones?.
Power Rangers' Alpha 5 is just to Robot Jones' left.
A little in front of Alpha is GIR from
Invader Zim. Next to him is that damn Mabus vacuum for some reason.
A little to the right of Humping Robot is Jenny Wakeman/XJ9 from
My Life as a Teenage Robot.
Behind her, Bubo the clockwork owl, and Calculon is Big Guy, from
Big Guy and Rusty the Boy Robot.
Following a line from Jenny past the robot from the
Hitchhiker's Guide movie and Rosie from the Jetsons, is Grounder, from the goofier Sonic the Hedgehog cartoon.
Diagonally between Grounder and Calculon is Octus, from the unfortunately short-lived
Sym-Bionic Titan.