This is a parody/tribute design based off the classic Calvin peeing decal found on cars .. usually peeing on logos - One of Bumblebee peeing on the Sector 7 logo not only made sense but was pretty bad-ass and something that I wanted to see.
A quick rundown of this image for those not in the know - there was a scene in the movie where Bumblebee "lubricated" (gasoline) all over Sector 7 Agent Simmons (John Turturro) during an interrogation for smarting off at Optimus.
Sector 7 (七番街, Nanaban-gai) is one of the eight sectors of Midgar in Final Fantasy VII. It also appears in some form in On the Way to a Smile: Episode Denzel, Final Fantasy VII: Advent Children, and Dirge of Cerberus -Final Fantasy VII-.
The Sector 7 slums is the first town visited by the party after the attack on the Sector 1 Reactor, and is AVALANCHE's home base and an unrevisitable location. The most prominent location is Tifa Lockhart's 7th Heaven bar. Denzel was born on Sector 7 Plate. Like every sector, it exists as both part of the slums and part of the plate. Only the slums section is ever shown in any Compilation of Final Fantasy VII media. (Source : http://finalfantasy.wikia.com/wiki/Sector_7)