I am going to try and make a treasure chest for my 4 (turning 5) year olds birthday next month. I am confident in almost all parts, but how does one get the fondant "wood-grained"? I found some impression mats of Global Sugar Art, but think they are a small pattern.

Any advise is appreciated!

I mixed 2 colors pale brown fondant (different tones) and mark the grain with sharp knife.
Then paint with food color mixed with essence several coat.

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1291730

Another example (the floor/cakeboard cover)
http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1249610

HTH