icloud Keynote image upload problem

Hi I'm uploading images to an icloud keynote document beign shared by several people, when i upload my images they appear blurry. But some of the images in the document uploaded by others look nice and crisp, Can anyone help me with a solution? I've tried uploading jpegs and png's at different resolutions big and small, same problem. Any help much appreciated! Thanks!

p.s I put this in the Keynote for mac topic as weirdly this forum doesn't provide the option of icloud keynote?....