Problems with fullscreen and graphics

I have for first time to do a fullscreen flash site - the SWF looks fine when its not fullscreen - but the vector logos that I exported as PNG files - look abit crappy when they are resized on full screen maybe my work monitor is too big - 1280/960 and my file is 955/600 - it uses the background at the top and the bottom - thats how the clients decided it to be
what should I do so the vector logos to be fine when the site is fullscreen - what formats should I give to the images - I used png till now for logos have transparent background images
Thanks for the help!