Thanks to everyone for sharing their thoughts and valuable links. It appears that there is no easy solution as of now, and maybe the initial assumptions were 'too fuzzy' for a precise answer. For this, let me try to refine the specifications:
1. The projector is intended to be used for the public presentation of photographs with the highest quality (in regards to color, contrast, sharpness) possible.
2. The room will be almost dark with no natural light and very dim (if any) artificial light.
3. The projection screen width will be varying anywhere between 2 meters (6.5 feet) and 7 meters (23 feet). Most of the time (95%), the screen width will be between 3 and 5 meters (10 to 16 feet). We're using Stumpfl Monoblox projection screens with Flex White CI screen material (gain factor 1.02, viewing angle: +/- 50°).
We've looked at various solutions such as Canon's REALIS WUX10 (LCOS), Leica Pradovit D-1200 (DLP), or JVC DLA-X3/X7 (D-ILA) projectors, but would appreciate some insight from experienced users.