This photo is courtesy of BCB reader tensionhead, who emailed it to me this morning. You still can't see anything much under all the plastic sheeting, but this gives you a view of it taken from one of the rooftops across from the right field bleachers.
It's also definitive proof that the Cubs are not building anything beyond the existing bleacher structure or raising the back walkway.
You can also see what appears to be some of the construction workers, either on a break, or more likely eating lunch, given that the scoreboard clock reads 12:10 (this photo was taken Friday, February 17).
Finally, this gives a better view of ... whatever that is covering the entire field. Looks like a tarp of some kind. Not exactly sure why the Cubs are doing that; I have never seen the field completely covered during the offseason before.
Click on the image to see a larger version. For an even larger version than that click here.