[Rich Cooper]

what's in the clue?
I've attached 2 pictures one of the original clue with the tone levels adjusted.
three areas of the picture were processed differently :
the "5" was lightened to bring out the diamond pate bumps showing through
the diamond plate was left original
the background was enhanced to bring the rather compressed range of data on the three (RGB) channels to full scale
A) in the original it look like we're looking through a blue filter that has been distorted by the diamond plate
what we see behind the diamond plate looks like
B) a large ball in the center foreground
C)in the lower left it looks like a smaller ball ( this could be a head but I think that is just jpg aliasing with the filter warp )
D)on the right hand side it looks like the edge of the playing field with another line for the edge of the crowd seating
E) above the ball there are three bands that could be large rings or hanging slings
F) between the bands we can see heads of the crowd on the right they are oriented vertically but in the upper left they are distorted to be tilted counter-clockwise whereas in the upper right they are distorted to be tilted clockwise

the second jpg is a guess of the picture with the diamond plate and the blue of the filter removed

What about the Diamond plate? First likes obscure clues. Others
have suggested a baseball theme. I will push that a little further.
diamond plate - diamond could both suggest baseball but also more specifically the diamondbacks - a 5 covering the plate would suggest the catcher
#5 for the Arizona Diamondbacks is Robbie Hammock who's historical contribution to the history of baseball is that he caught #51 - Randy Johnson's (the Big Unit) Perfect Game ( the 17th in MLB ) in Atlanta on 5/18/2004

odds and ends: the 12 diamond repeats across the circle => 18" circle
the "5" font is bold arial

What's it mean?
Game Name - "the Perfect Game"
Game pieces - large and small balls
Goals - rings or hanging slings ( Hammocks )
field - 4 goals at center of each side + one center of field ( 3 line up as in picture) center of field raised diamond plate platform ( pitchers mound )
BLUE and RED Lights above goals to say which are active for scoring for either team ( from Blue filter )
other - if the diamond plate - "manhole cover" is hanging vertically as in the picture it could be used to toggle the lights on the goals