Thank you for all your comments. If I might answer:
1. I agree about image size. I decided to limit the size of the main image to 600x600 pixels for a couple of reasons:
a. Most architects, who are my target, use laptops/notebooks or smaller desktop screens on their desks. The larger monitors are at the studio workstations, where internet access is limited to team leaders. I didn't want users to always have to scroll to see the whole image.
b. A recent PhotoShelter survey says that most photo buyers like an image size of no more than 700 pixels, which also minimizes page loading times.
c. Andrew, if you know of a way to scale images for monitor size, I'd appreciate if you could give me some advice. I did search, but couldn't figure out how to do it. I designed it myself using Kompozer.
d. I will link larger images to open with a right-click.
2. Feppe, there's always an arrow visible under the thumbnails, so would it still be easy to miss it? I wanted to see what the viewer experience would be before buying the Pro version of SimpleViewer, which will get rid of the logo, as well as let me reposition the arrows. One problem is that it needs Adobe Flash to edit the swf that SimpleViewer generates. While the editing can be done within the 30 day trial period, any later editing would require me to buy Flash, which I really don't need for anything else. Does anyone know if/how this can be done?
3. Re: Flash vs. HTML. If there's no Flash or Java enabled, a message with a link to an HTML gallery shows up. I expect most of my target audience will have Flash enabled.
Thanks,
Kumar