here is a signature i made with 400x130 and the second is one with 300 by 130 not much bigger its basically just adding 15 pixels
This one is 400X130 its not much bigger but gives more space to work with
This looks big but its actually smaller 300X130
The point im tryin to make is. A bigger size would be a great idea. and i say this for a few reasons. Also i think that 500 is to long for size. it streches the page i think anyway. plus from a gfx point of veiw looks nasty. And you may say for certin user groups well why not for everyone. well i dont mean to sound mean but. we dont have to cater to everyone. people who dont use there best judgement and put a massive picture on there sig should recive a infraction.slow page loads come from them.
I sure hope you decide to up the signature size it would be greatly appreciated from alot of us at AO ^_^