is 1600x1200 okay or do you need bigger? if you need bigger i might not be able to help.
also - i stumbled upon a pdf of "Exploring the World of Aquatic Life". theres a ton of images that you can export from the file. the output of the size can vary since when you export you can set certain parameters.
i use PDF-XChange as my viewer / editor of choice. if yours has the ability to export pages this way then you might find something in there that you like. send a PM if interested.
if i come across anything else, ill let you know.