I worked on a geographic data visualization application that leveraged a spatial wand input device. A unique feature of the application was fluoroscopes, data lenses that could be moved around and resized on the map. Each instantiation of a fluoroscope was tied to a particular geographic dataset and configuration, like doppler radar. The user could create as many fluoroscopes as they wanted and arrange them on the underlying map.
Some fluoroscopes didn't load immediately, so we designed feedback to let the use know the geographic data was loading. Progress bars weren't technically possible at this stage in the application's development, so we opted for a more stateless solution.
I liked many of these initial ideas, but in gathering feedback from others I realized that many of these would be hard to use when the fluoroscope wasn't large and completely on screen.
I decided to go with a light, transparent background with an opaque banner to not obstruct the underlying map, but keep the messaging legible.