The WUnderground Plugin Gauge Pack is a series of nested folders containing graphic components that can be used on Control Pages to build gauges for select WUnderground Plugin devices.
All images are PNG files and can surely be used for other purposes (i.e., other Indigo devices, etc.) but the naming conventions are geared towards the WUnderground plugin itself.
This is a fairly large file (about 12 MB.)
Installation instructions can be found in the WUnderground Plugin forum.