Two years ago I wrote a small converter (TIF2LCD) to convert 128x128 TIFs (BW, not compressed) into a file from which I could paste image data into my source code. Image data then looks like this:

DB 01,02,03,04,05,06,07,08,........................16
DB 25,26,27,28,29,30,31,32,........................30

(if you're interested I could send you the C-source, but it's very simple)

That was an easy way to get any picture onto a dot matrix LCD. For converting an image into the GIF you can use any image application that is able to change the pixel resolution to fit your LCD resolution. Under OS/2 (the best OS in the universe) I use the great PMVIEW for this.