Actually, I probably have some of the largest image galleries on the web. I've also developed or contributed to many image programs and gallery applications since 2003, quite possibly even the one you've adapted for your site.
1- the Google Ads are refreshed while browsing the gallery
relates to html, not adsense
2- With no database
relates to php, not adsense
3- Images can be indexed by Google Image bot
relates to htaccess, not adsense
If the question is, "does refreshing ads work better than fixed ads"..
There are a lot of different opinions about replacing ads on each image page load. Some people swear by ajax image loading, reasoning that the longer an ad is in your face the more likely you are to click. I try to avoid ajax as much as possible in my image display applications because I find fixed ads don't do as well for me in those settings. By showing more ads, it's more likely they'll see something that interests them. You may find your CPC suffers a bit as a result though.
At any rate, sourceforge will have what you need to get started. There's still no perfect solution for displaying all types of images in all settings so you probably will have to customise a bit for your own needs.