In a few weeks 30 billboards will display a new URL in the local community (200,000 population). The URL will point to another site with all the real content, so this is just a splash page. The whole thing will be a graphic. Having said that, is there an optimum size I should use. Now that 17" CRT's are selling for $5/each on CraigsList, a lot of folks are getting 19" wide-screen LCD panels ... so, what should my target be. FYI, the splash page/graphic will have about 1/2 of the content in text, which will probably be 50-80 words (don't know yet).

make the image 960px wide, it should be sufficient. With bigger images come bigger filesize and so more bandwidth, so I think you want to keep the image < 50kB.

That issue has been argued about for years. There's really no right answer. I would think it just depends on your target audience. I've done sites anywhere from 800x600 to 1024x768. I usually try to get a feel for what they want and what i think the populous would use.
For a gaming site, i'd use a 1024x768 resolution because gamers normally like to keep up with current hardware and whatnot. If i were designing a site for someone that's trying to sell products or market products i would probably design for 800x600 because that would cater to older folks who don't really care as much about their computers. Also, i'd do the same for medical websites.

Just try to get a feel for who you're catering to and go from there :D

Never mind, i just re-read your topic and i misunderstood the question :/ GO ME!