Here are some things to remember:
- The closer you place a light_spot entity to a brush face, the 'harder' the 'edges' of the cone will be, and the more jagged they will look. If you move them away, their cone edges will be softer but you will have less control over the shape of the cone and the pattern of brightness.
- When a cone hits a dark wall, the contrast between the dark surface and the light cone's edges can exaggerate the jagged effects. You can improve the look by including more light entities in the area to brighten up the wall, so that the jaggedness becomes less noticeable.
- The light thrown out by bulbs in those light fixtures probably don't look like that in real life. You can afford to be a little messy.
If you want to simulate an attractive cone effect, without increasing the lightmap resolution so much, and you don't mind so much what the shape looks like, then you can move the light_spot entity a bit further away from the prop, in a 45-degree direction. And as YM says, put in a 'phantom'/fake
light entity near the prop to simulate the brightness of the bulb.
This wall has a lightmap resolution of 16 luxels (default).
This wall has a lightmap resolution of 8 luxels. Notice the smoothness of the cone's edges.
In the screenshots I used a point_spotlight entity above and below the prop to simulate the point of light that is the bulb.