Increasing Mavericks Time Machine backup size for remote backups
Here's what you need to do to resize an existing Time Machine sparsebundle without loosing data on a Time Machine server (OS X Server):


Turn off Time Machine Server.
Turn off Time Machine Client(s).
Resize the disk image and the partition following these instructions. Execute these steps on the server, where the drive is attached if possible.
After 3 completes, turn on Time Machine Server.
Remove backup destination on client and add it back.
Turn on client Time Machine and perform a backup.


I followed these steps and I was able to increase my backup destination from 1TB to 2TB without loosing backup history.

Here are a few issues I ran into and how I worked around them:


The Resize Image icon was greyed out in Disk Utility. This was because my logged in user didn't have read/write access to the sparse bundle. Rather than change those permissions, I logged in as that user and could resize image.
Nothing appeared to happened after I told Disk Utility to resize the image. This is apparently a defect in Disk Utility. While there are no indicators resizing the image worked, if you go to the partitions tab, you will see the image was increased.
It took 4 days to complete. Increasing the partition size appeared to have kicked off a disk check of sorts. That process and checking multi-linked directories took about 4 days to complete. This was on a directly attached 7,200 RPM drive array attached via USB 3 with about 1TB of backup history. I don't know of any way to speed this process up, so just be aware it may take a very long time.