Need images cut out professionally, put on white background at 500px x 333px....

Design details: I have about 150 images in different formats, sizes, backgrounds etc. I need them all cut out, placed on a white background 500px (wide) x 333px (high) and all to the same ratio of image to background which is demonstrated by the attachment (image should try to be placed in green area). Anybody submitting for this job will need to complete the test image to show ability. If able to watermark our logo attached into it that will be great. The test is the image with the yellow background and please note this is probably the toughest the majority are in a mostly white background anyway.
Ideas for the visual style: As description
Extra notes: