As chrisbarela said, few reptile houses avoided the boring "row of tanks" design.
Best houses have semi-open exhibits for turtles, crocs, but also large lizards. There are even walk-through areas for tortoises, iguanas and small lizards and frogs. Rangers in Denmark and I think Budapest even have walk-in rooms with some free-roaming non-venomous snakes.
For small species, best examples join multiple glass tanks into larger habitat exhibits, like Arizona-Sonora Desert Museum. They can be linked into one with decorations in visitors area. At best a visitor walks though small simulated habitats with reptile exhibits set inside them.
Always most important is careful design. With reptiles and amphibians, you can recreate fascinating, detailed little habitats, with little rainforests, deserts, bushland, wetlands etc.
Rather different approach is in Sea Life Centres, which have small tanks in different shapes: half-bubbles, pillars, overhead, see from above etc.
In design and maintenance: off-exhibit keep it open, avoid any narrow spaces and holes where runaway reptile can crawl into or escape through. In exhibit be able to precisely control temperature and humidity, avoid drafts and lack of ventillation. Reptiles are sensitive to just few degrees of temperature difference. Set staff doors to exhibits above the ground to minimize escape risk. For smaller but escape-prone or agressive species, good is the ability to divide exhibit into half with plastic sheet etc. during cleaning.
And another - for visitors, ability to hold and touch presentation reptile is most interesting.