Is there anything like this, or a server tool, that lets you see what mods/texture packs or whatever people log on with or kick people who log on with certain ones?
No. Client mods like griefing tools, will do their best to prevent the server from knowing they are using one.
As stated in the Plugin Request guide which you were supposed to "READ ME" but of course you didn't read it. It says: Make sure your request is even possible. Bukkit plugins can, for the most part, only modify what the server can do. Here is a list of things you cannot do with a plugin: Create a new block or item. Show a picture or video to a player (except maps or displayed in blocks) Create a new creature or monster or change the size of an existing one Check if a player has a texture pack, mod, or hack installed. Play external sound. Can only trigger noteblocks, records and effects. Move a player between servers (in a way that doesn't involve complicated proxying)
No, you can do some clever magickery that will utilise textures/blocks ids already implemented into the client to give a block new mechanics. This is not the same as creating a new block
