Ok I have a few plugins that could be added. All the links will be at the bottom.
Core protect- This is an anti-grief plugin. What it essentially does is do 'rollbacks' of when people place or destroy blocks. The command is /co i, so if I were to left click a block it would show who placed that block. Or a right click would show who removed a block.
Tablist Prefixes- This explains itself, instead of having a prefix by your name in chat it'll have your tag in tab and above your name when someone looks at your player. To me it makes identifying players easier. If a new player looks in tab for example they wouldn't need to go to spawn and search for the staff heads when they can simply look in tab and /msg them for help.
Clear Lag- It's simple. All you need to do is configure a specific time and clear lag will wipe all dropped entities throughout the server. It will also come in a 40 - 20 - 10 second warning for players and staff to prepare so they wont lose their valuables.