I am going to have to edit my post above. After exporting files from Dropbox - it went to Nook's internal memory which was not what I thought it would do. I purchased the Drop2Sync app and now use it in conjunction with the Dropbox App and these files do go basically to files that are accessible. My pictures did go to a picture file but my wallpaper also went there as well. I have not yet tested music or books - so those I am not sure of yet. But at least they go somewhere that you can find them! I guess Dropbox would be better used with an SD Card - but again that I am not sure of - since I have not yet started using an SD card.
I also use the Dropbox .But instead of transferring pics to my nookcolor, I have been transferring information from my writing app, journal, and devotion apps to Dropbox. Most apps give the email or dropbox options. I prefer using dropbox because it holds so much more files and is accessible from any computer with a click of an icon.