Lite Control Center - Suggestions welcomed

[UltraCookie]

I only added the Spotify and Inkscape repos as far es I can remember.
The Spotify repo causes some errors when updating. They come and go and since Spotify doesn't get many updates I tend to ignore it.

Code:

W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used.
GPG error: http://repository.spotify.com stable InRelease:
The following signatures couldn't be verified because the public key is not available:
NO_PUBKEY 13B00F1FD2C19886

W: Failed to fetch http://repository.spotify.com/dists/stable/InRelease 

W: Some index files failed to download. They have been ignored, or old ones used instead.

APT Policy:
http://pastebin.com/W0nNycBR

Code:

ls -l /var/lib/apt/periodic

Output:

Code:

total 0
-rw-r--r-- 1 root root 0 Jun 17 06:38 update-stamp