I see your bug... (aside from correcting MemberQ[i,bbs] to MemberQ[bbs,i]). (Again, I really didn;'t read your code in detail--sorry!) This is that your

Import["i.tiff", "Data"]

needs to be

Import[ToString[i]<>".tiff", "Data"]

in your original "i.tiff" this is just a string. The ienter code here in it is just the string character and has nothing to do with your index in your For loop.

I will admit that I did not investigate your code much more than noting that you needed to correct the MemberQ[bbs,i] call. (See http://reference.wolfram.com/language/ref/MemberQ.html to review the correct form of the arguments.)

So your next step is to see if the Import function is seeing the files you are asking it to import. Take one such file, say 40.tiff, and try importing it simply by calling

Import["40.tiff"]

if this returns $Failed then Import has not found the file. Why might this happen? When you don't give a full file path to Import, Import is looking for the file in the directory returned by

Directory[]

So you now have two possibilities (assuming that the file 40.tiff actually exists!). One is to change the value the default directory using SetDirectory. The other is to provide the full file path of the file you want to Import to the Import function.

MemberQ[bbs,i]