Database Issues
If you are experiencing issues with the database, you can clear out (and thus reset) the existing database by entering this in Terminal:
rm -rf ~/Library/Containers/com.deckedbuilder.deckedbuilder
For Android, you can delete the images in this directory:
/mnt/sdcard/Android/data/com.deckedbuilder/cache/images/
or for Decked Drafter you can delete the images from here (on your SD card):
/Android/data/com.deckedbuilder/cache/images
Note that this directory (/Android/data/com.deckedbuilder/) is the directory that decks have to be saved in for the app to recognize them.