There's also an open source vector based image editor (think adobe illustrator or whatever) but for the life of me I can't remember the name of it.
If you want 3D drawings/renderings you can use Google Sketch-Up (I used that to draw up the plans for the deck and wrap around walkway I built at the in laws a few years ago using free wood too! Lol. Had to have an outline of the plan to get the permit)
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