Customized Tumblr Theme Needed

I'm looking for someone to take an existing template and customizing it even more. This involves mainly - add share buttons to every post, such as facebook and twitter and allow people to add notes - have the picture add in a lightbox for when the user clicks on images, the image expands - create the ability to customize the background - freeze the background as the user scrolls up (fixed background) and some other minor alterations that we can discuss. Please have experience with making tumblr accounts. You may be asked to provide an actual sample given that I have had with previous service providers believe they can do the work, and actually can't. Thank you for submitting your bid.