Question requester deems the below analytical information is less applicable now that the requester would like to narrow requirements.
Here's a shocking open source web based and email capable request management application i just found for you.
It is FREE - check
Dashboard feature - check
Email feature - check
non user self service- check
I like that there are O'Reilly book on it for you to get the support you need.
*It let's you reply out of inbox, it is web-based so it goes across mobile platforms as well, non-user self service logging interface, organizing around projects/categories... almost too good to be true. I'd be very curious to hear your trial result if you decide to try it.
Shockingly also, great organizations use it: NASA, Merill Lynch, Kayak.com, Nike, MIT (spells out respectful and versatile to me)
I didn't find any info on image integration yet... which sounds pretty useful for your industry.
Sounds like there are three major requirements (ticket lifecycle processing should be included) :
1. a ticket logging email notification mechanism
3. client engagement and participation
It's actually difficult to get all three things together. It's very easy to have a cheap notification system, even if it is a simple Google Form to get the ticket logged and distributed to all members. Then a CRM or a ticket management system can take care of the ticket processing lifecycle from open to assignment to close etc (generally included).
You need to specifically check Dashboard feature because most only have very basic table / excel like reporting. Dashboard can be an expensive feature.
Finally client engagement is even harder because you need to give them access to your ticket management system, involves a lot of user right specification and you need to train them how to... gets pretty messy
I would say since your team is still relatively small, try software-as-a-service providers then you don't have a to pay a high premium. If you want all your features together, may be salesforce.com CRM type of ticket and relationship management can be a good fit. I think their newly acquired Chatter is especially interesting that allows multi-staff collaboration and also can invite clients to join the chatter thread and view progress and get involved. But it may comes with quite a price tag. Their sales team can be aggressive in pursuing you during or post a trial.