Assuming that all the online heraldic shield generators are not giving the style you want already then I would do the following:

If all the shields are the same size such that the logos for them will all go into the same position to look right then you could code that up just using HTML and PNG files with clear backgrounds. Then by using a form and a cgi script to write them out you could have a web page that you select the icons and it would make it. There is no need for flash programming.

If this were me and I had to do this such that it could be scripted then I would use image magick which makes this sort of thing real easy.