Sign artist is a perfect way for your members to use images from the world wide web on signs ingame. However, some users might use this command for bad intentions. They upload some ww2 content, some adult stuff or images you do NOT want to have on your server as a server owner. Therefore, this idea.

TOS GUI

When the command /sil is been triggered for the first time, they firstly will be getting a popup with a reminder of fair usage and by keeping it inside the rules of the server. They can accept the terms or reject them. When they accept, they are granted the needed rights for the usage of sign artists. If they reject, they will not be able to use the sign artist command.

The server admin
the server admin can revoke the rights of the specific user if the player has broken a rule on the server depending on the usage of sign artists commands. By using a command, the user can be banned forever for the usage of sign artist or temp locked out until certain XX days. 

Blocked

If the user is being blocked for further usage, the admin can decide the following.

1. Mute/Ban the user for further usage of signartist.
2. Mute/Ban the user for further usage and delete other signs that are placed by this player.

signartist.accepted
signartist.denied
signartist.blocked​

1. When a player its rights are revoked for the usage of sign artist, a message would show in the chat that the user has been blocked for further usage due to [reason]
2. An admin can use /sign history [playername] [number] to see what the user uploaded before. (Is a webhook discord an option for that? i bet it would save the server some breath somehow as well ) 
3. An admin can use /sign delete [playername] to delete all his uploads to signs ( in case its a spammer ) 

Is someone still maintaining the plugin? 

What a wasted suggestion. pitty.