Although, no heraldic artist myself, I do emblazon some shields for my own benefit.
I would offer the following advice. Firstly, is Wikipedia. Everything on Wikipedia is copyright free. If you go to
http://en.wikipedia.org/wiki/Main_Page; go to the bottom of the page and click on "Commons"
, or go straight to
http://commons.wikimedia.org/wiki/Main_Page this will take you to a great repository of heraldic images.
Type heraldry in the search box. The first problem now occurs - there is no rhyme nor reason nor logical categorisation for all the images. The whole thing is like Topsy - it just grew and grew! But, perseverance pays off and if you search for the right things, you will find them. Any search should be "XXXX in heraldry". If you search for Fess, you may or may not find any. But if you search for Fess (or Fesses (I know)) in heraldry, you will find 10,000.
Having found your image, click on it and get to the page for that image (each image will have a separate page. If the image is SVG, under it you will find various size options. Click on 2000X - (you can make it smaller and it still looks good; make it bigger and it looks rubbish). Save to your hard drive.
You need an image handling programme. I use Paint Shop Pro - it was free and it does the job. I work in MS Paint, but it won't handle the image you have just downloaded, by itself. I open it in P S P and then copy it and then paste it into Paint. Then you can do with it what you like. I always save as a PNG file and can edit it in Paint any time after that.
There is as well "Inkscape", open source and free to download.
http://inkscape.org/ Some say that it will do as good a job as Photoshop. There are tutorials on line and forums. Give it a go.