Hi Marion and welcome to our forum!
We'd be happy to help you with your project. In fact, we have some components that will help you complete this quickly. If you would like to leverage our expertise and tools, please send me e-mail by clicking on the e-mail poster icon at the top of this post.
Alternatively, if you intend to do the design and development yourself, please feel free to continue posting questions in the forum. We have done hundreds of forms. Your requirement about locking the comments and allowing for asynchronous updates, etc. suggests that you may be best off using a SQL database. In addition, there are several known limitations with SharePoint (flat data, scalability, permissions) that may pose challenges down the road. My suggestion would be to leverage the new version of our Qdabra Database Accelerator Suite (BASIC version is FREE) which will enable easy integration with SharePoint and support digital images with no problem. Plus, you get a huge head start on the development. With the suite installed, you will probably need between 20-40 hours of work to build the solution, design the reports, and configure the workflow. Let me know if you are interested. We will be releasing version 2 in the next few weeks. We have many people on beta now and I'd be happy to send you the most recent build.
Patrick Halstead
Project Manager at Qdabra