Read the thread
[Link: remotecentral.com].
There are lots of places on the web to get channel bitmaps, for example satlogo.com/tvcountry/us1.html, brandsof the world.com and the web sites of providers like directv.com.
That said, many of the pcfs available for download on Remote Central have incorporated channel logos. The designers of these files have already "optimized" size, color and detail, and placed a border around the graphic. To get the best pictures for the least amount of work - plagerize!
If you insist on doing your own, you can automate the process of sizing, establishing background color, adding borders, etc. using the macro facilities of programs like Paintshop Pro or Photoshop.