Please supply the following:
A PNG file with its longest side length under 250px.
Do not use transparent backgrounds, but if your logo is not rectangular please set it on a white or very light grey background. The image may be resized smaller so do not depend on very fine detail or small lettering.
A paragraph or two of plain text for your sponsors page.
This will be displayed when users click on your logo on the web site. This may be edited slightly by the FOSS4G LOC.
A URL for a link from your sponsors page.
This can be your home page or a page within your organisation.
Note that further graphics files in higher resolutions may be required for print and display purposes. If you have the logo in a higher resolution PNG (at least 720 pixels across or high) or in a vector format then supply that as well as the low-resolution image suitable for website usage.