I recently received a request to review this iPhone application, which is tagged as being a “support and clarification in communication with people with a (mental) disability.”
iPicto definitely has a large database of images (more than 4000).
Most are very basic in nature and could be considered stock illustration.
iPicto was very unwieldy however; the interface was not well thought out and as a person without a mental disability (to the best of my knowledge at least), I had a hard time with navigation.
If you want a large stock illustration app, consider buying this. However, if you need something to aid in communication with Autism, Asperger’s, or people with other communication disorders, I cannot in good faith recommend this application.
If that is what you are looking for, check out this post on Autism applications for iPad and iPhone.
Also, if you have an idea for a great iPhone app, feel free to get in touch with Apprepro for your development needs.