Yes, of course you can. The SVCD specs allow you to add extra stuff to the CD.
Put all the extra files you want on the CD in a folder and save to your HD. If you burn the mpg files out with VCDEasy, just go to the ISO Files tab and hit Add Folder and select your files. Do NOT add any files to any of the existing folders on the svcd cd, else it just wont work in anything.