Nice conversion method
When converting a PDF with pictures for an ebook device, I found a good method with minimal fuss. It is a bit time consuming and you need a 3rd party product.
Use ABBY Finereader to convert to LIT format, then convert the LIT to the ebook format of your choice. Pictures will be preserved. Abby Finereader takes a while to convert for its own format, but it will also handle scanned books. I have not tried 2 column PDFs, but an average PDF with pictures is OK.
I then use BookDesigner to convert from LIT to LRF and the result is quite good.