>>My concern, however, is that eventually there will be a lot of pictures meaning a lot of new pages. >>
I do the same thing on my Web site. I have about 500 photos and accompanying pages. I went this route quite simply because it looks more professional than just having it go to an image file.
>>Doesn't this solution use a lot of overhead? (storage space, loading time, etc.) >>
The HTML pages themselves are only about 4KB. The overhead usually comes from the image files, which tend to much larger. I keep mine restricted to 30KB and under, which keeps the load time down. The big advantages of using the HMTL pages is that is does look better, and you can use keywords in your Heading 1 tag, which carries weight on search engines.
You can make things a lot easier for yourself by thinking about the organization of the files. These are things I've learned through a lot of trial and error:
Use a naming convention. Name both your photo and the page the same thing--i.e., below01.html and below02.jpg to make them easier to find.
For single digit numbers, use a zero and then the number or they won't sort properly.
Keep the naming convention simple and use words you can understand.
Organize them into matching folders (i.e., a folder called below).
I took it a step further. I only have about 12 thumbnails to a page, with each linked to a corresponding HTML file. For each new thumbnail page, I created a folder and put the thumbnail page and all the corresponding pages into it. In my case, it's below/01. That helped me keep better track of all the files and cut down on the number of orphans.
Finally, I run the Unlinked files report periodically to make sure I don't have any orphans.