Lighting fixtures (20) for attachment to architectural surface structures are adapted to hold light sources (100). The lighting fixtures (20) may include a base plate (32) and mounting brackets (34A, 34B). Clamps (80) are provided that may bias the light source (100) in either the forward or rearward direction. The clamps (80) may include spring arms (92) that center the light source (100) within the fixture (20) in addition to retaining the light source (100) in place. The fixtures (20) may further accommodate overlying structures, such as lenses (350). The lighting fixtures facilitate use with a variety of different architectural structures and formation in various shapes.