A lot depends on what you want to carry, and how far you want to carry it. Very different for something that stays in the truck next to where you cut, and something that you pack in on a trail. A box with a lot of spare parts gets big (and heavy) fast, and might belong back at the basement or shop.
There have been a lot of posts with photos of very creative tool boxes here on A.S. Some are buried in threads on saw storage, or chain storage. Lots of comments on using pickup trucks as tool boxes. Plywood is easy to customize but gets heavy quick.
I have a few different saws and try to keep a few extra chains and basic parts (spark plug, bar nuts, etc.) in each saw case so that they are with the saw when needed. If you don't use saw cases, you might have a smaller, basic box for a few files, essential spare parts, etc., and another box for tools that you are more likely to keep in the truck or use in the shop than carry into the field.
Here are a few related threads to root through. Keep playing with the 'Search' tool to find more.
Philbert
http://www.arboristsite.com/firewood-heating-wood-burning-equipment/89533.htm
http://www.arboristsite.com/chainsaw/181807.htm
http://www.arboristsite.com/chainsaw/178537.htm
http://www.arboristsite.com/firewood-heating-wood-burning-equipment/171234.htm
http://www.arboristsite.com/chainsaw/125133.htm