I've been trying to finish my layout, and I was wondering if it was possible to set a background image inside of a table?

You can, though I would definitely not recommend using tables for your layout. You really want to go with CSS. But since you asked so nicely, here is some code that will help you out:

<TABLE background="yourimage.jpg">

- Steve

or you can use this:

<table style="background url('images/my_image.jpg')" border="X" width="X" height="X" alt="MyImage">

Replace all "X" with your desire needs and properties of the image.
Hope that this helped you

Shouldn't that be

<table style="background: url('images/my_image.jpg')" border="X" width="X" height="X" alt="MyImage">

(missing colon)

yeah forgot it. xD. Thanks for the correction

Everyone above has showed you how to include the image as a background in a table.

But one important detail that you need to remember, is that if you are making it as a background, then be prepared and make sure your image can stretch. Because if you don't set specific widths for tables and cells, and start inputting text then the table is going to stretch and there for your images will start stretching and if it is not meant or designed to stretch it will start to repeat.