I really cannot see from the picture, I have had a similar problem on a car a few years back, in which the flex plate was cracked. The car would clank and sound like crap at idle, however at higher rpms the sound would go away.
When i pulled the flex plate i found that there were cracks around the bolt holes that attach the plate to the crank. The cracks looked fine but they were present on both sides of the plate. Based on the thickness of the plate i could not force the cracks open or anything like that.
I expect that cracks in other places would cause the same issues.
Hope that helps
1993 Camaro Z28 A4 (4L60 non-"E")
K&N CAI, BBK TB, Superior Perf. Shift reprogramming kit, Corvette Servo, NGK TR55IX plugs, Taylor Cable Thunder Volt 8.2mm wires, founders perf rear LCA & PHB.