Format player

Hi all,

I would like to know if there is a way to format the appearance of the player, other than changing colours and transparency options - specifically, I would like to change the shape of buttons and things, and the player itself. 

I would like the default prev, next and submit buttons to have to have square corners, rather than rounded. As well as default pop-up boxes - square corners instead of rounded. The client I am working for hates the look of rounded edges, and insists that I change them.

Please note I am not interested in creating my own custom prev/next buttons/popups etc. as I have already done this for the most-part, but there are some cases (such as on full-screen video slides) where I cannot fit my own buttons.