I assume some of these photos are applied to polygons placed on top of the main building polygons? If you mean these overlay objects are flashing as you move around them, this is due to Sketchup placing two polygons essentially on top of each other. FS does not know which one to display, so it flashes back and forth. You have at least three possible solutions:
1. Move the outside polygon (usually windows, etc.) further away from the bottom building polygon. This will lead to potential visual issues when close to the building (i.e. you will see the outside polygon).
2. Make a custom texture with the window (or whatever is on the outside polygon) as part of the main building texture. Then the extra polygon is not required and you will have no flashing.
3. If you are compiling to FS9 or P3D, you can use a Bias value in the MCX Materials Editor to increase the visual priority of the outside polygon. You can also do this with FSX but MCX just moves the polygon out a bit, since FSX does not have true Bias control. But this may be an easy way to do choice #1 for FSX.