Hi Scott,

For now there is no such option to do it from the table menu. We will add this option soon.

Meanwhile as a temporary workaround if you familiar with HTML I can offer to you:
1) make a copy of your .IOK file and do the following with your copy,

2) in the Content View insert your new background image just as a simple image somewhere near your table,

3) switch to "Edit HTML Source" mode ("< >" button),

4) in the code, find < img > tag with your new background image, e.g.:

< img src="embed://image/2.PNG" border="0" >

5) find < table > tag with your table, e.g.:
< table cellspacing="0" style="background-repeat: none; background-image: embed://image/1.PNG" class="tlbrSmartBorderPale" top="#DEFAULT" cellpadding="0" >

6) change the name of the image in your table for what you have in < img > tag, e.g.:
in the example, change
"1.PNG"
to
"2.PNG",

7) if you want to change the size of the table with new background image you can find a line with width/height in pixels below table tag, that should look like:
< td valign="top" align="left" width="481" height="160" >

change the width/height corresponding to the size of your new background image,

8) switch back to the design mode by "< >" button,

9) now you should see your new image as a background of your table.

Great - thanks for the work around