As long as they are completely cooled I don't see a problem!! You could also do a fast freeze for say 20 minutes.And then decorate
I bake, cool, decorate and then let the cookies set out until the frosting firms. The cookies are usually cool in less than 30 minutes I would say. The frosting takes longer to firm and I don't stack them until day two. I usually drag out all my rubbermaid/tupperware containers and single-stack them and cover them up until the frosting is completely firm for stacking. Does that make sense? If I wanted cookies for Sunday, I would have decorated them Friday night or very early today. I have also heard not to use wax paper when stacking since they may stick and that parchment paper is better. Hope that helps. It's what I know so far from scouring through the forum here. 
kos
I agree, the waiting time to ice cookies is not very long. Ofcourse, you do want to make sure they are cooled but I think even just a half hour to an hour would probably be fine. Just check to make sure their cooled!! The longest part is waiting for them to dry after their iced to stack. I usually do the same as suggestedbyKos, put them somewhere their protectedbut not covered for atleast 8-12 hours BEFORE you stack. I usually make sure I have one extra cookie as my TESTER.
No, No Kos, I said one tester cookie that means to check for dryness. At that point I would have had one (or so) to check if they tasted alright and THEN one tester to check for dryness that would get eaten AFTER it was used to make sure they tasted good with the icing on them. LOL
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