I went into a world where there was three item frames on a wall, which caused my 60 fps to go down to 1-3 fps. If the item frame is not rendered, there is no effect. In the item frames, I put some pretty powerful enchanted items (given with command blocks). However, this also happens with an item frame with nothing in it. This didn't happen in 14w03b.
Related issues
Attachments
Comments
migrated
[media][media]
If this is unique to 14w04a (try the world in 14w03c to compare), it would likely be a duplicate of MC-45458
galaxy_2alex
Might be related, but this looks like a legitamate bug to me.
Basically: Placing Item Frames in the Chunks of spawn protection lags out the world.