what are some allowable mods riot allows?

Aesthetic stuff.

I think voice chats (and recorders) are as far as they would allow, even then, not all of them are approved.

Anything to do with actual game mechanics would be banned, which also include timers.

#LoLwiz I have a code you can use. :p

Generally speaking, all allowable mods are allowed.

Can't remember the site but it was like lolskinutlimate something like that which you could download skins but only you could see that skin.