Backstory: I recently ran a 5k race in Baltimore, MD. The organization had a photography team come and photograph the race. About 24 hours after the race, photos were uploaded to the photographers website. I was stunned to see that I could search for my bib number and find every photo that I was in. I contacted the photography company and asked how they did this, and the owner told me that have to do it all manually. Every photographer is responsible for manually tagging their own pictures with the bib numbers in those pictures.

The Idea: Photo tagging software for race photographers. A CMS/online store for this would be ideal.

Deep Dive: This is a huge idea that would take awhile to build and perfect, but you could start small. Create a CMS/online store for photography companies. The CMS would allow photographers to create an account and upload albums for race events. That's it.
Once that's done, you could add the most important feature: image tagging. When this feature is implemented, each photo would be automatically tagged with the bib numbers shown in that picture so that users could lookup all of the pictures that they are in.

Validation: The amount of hours spent uploading and tagging photos for races is ridiculous. The photography company that I contacted didn't give me an exact estimate, but said that it often involves photographers working "into the night." This could be a way for those companies to save costs and time.

Monetization: You could charge a percentage of the photography companies revenue generated from the software, or you could charge them a monthly subscription fee.