In a lobby, I would look towards a more architectural based G-12 type metal hallide
HMI Leko. Such fixtures project images well and have very long lamp lives. What brand between
Altman,
ETC or others is up to you and the price, as with going mini-Leko or normal Leko in size. For perminant install as long as you optimize what projection size you need for the fixture it's going to work. There is also some other types of projectors that might be more reasonable in price. If it's a question of a perminant projection, you will be most cost effective in going with something that's designed even engineered to project things than something you come up with.
The G-12 based lamps based around the Philips CDM lamp are available in two main color temperatures that are directly relatable to that of a stage Leko, only the hours of life are much better thus more cost effective both in wattage at 150w, and lamp life. A type 830 lamp will be a little more amber and dim than a S-4 with a HPL 575w/C lamp, and the 942 style will be more bright than that same fixture and lamp.
Go with a CDM-SA/T150/942 lamp, it's for the most part the most cost effective bright lamp. GE actually makes the brightest lamp of the type, but Philips in being most available will probably be cheaper. Otherwise the most high output/color temperature lamp available is the Osram HSD 150/70 lamp. We are talking better than follow spot in color temperature but more limited life.