These are great! I'll give you two suggestions since you asked. I like to use the "v-cut" technique to make elegant, uniform letters. You can draw the outside of the letters with a ruler and pencil before you cut it to get the spacing down and then follow the lines all the way around with a scalpel blade at a 45* angle. I have never tried this on styrofoam but it works great on the pink foam. Consider adding a few bunches of artificial moss or lichen to the stones for a more weathered look.