With Yosemite, when I scroll the corkboard, when the scroll stops, a new corkboard is painted. The painting is unnecessary, since the corkboard is already correct. But it’s annoying because the new corkboard is different from the old one, so you see it change every time.
Yeah, this is a known bug, it will be fixed in the next minor update. Apple changed the model used to position graphics in a view. You can “fix” the distracting part of it right now by choosing a solid background fill instead of a texture, in your Corkboard preference pane. Sorry about that!