The best person to gauge whether Omeka works for your project is you. If the presentation works, and you like the flow of adding items, then use it. Omeka has been used for a broad range of projects.
You can definitely add more than one file to an item, however Contribution generally only collects one image per contribution. There are workarounds - asking people with multiple images to get them to you another way, or by changing the code, as discussed in this forum post.