I think a simple paint program so you could make your own towers and bullets and creeps would be awsome, still keep the premade ones but people could make there own designs to, maybe even feature some of them on the portal. But it's nice and simple and I like it.
The building aspect of the game was very easy to use and very nice however the actual tower defence could use a bit of improving. Perhaps looking at some of the more popular td games on the site to see how u could improve the overall game. Pretty fun and a decent attempt :)
VERY good idea! You´ve practicly created an endless source of TD games, rich in variety. There is but one issue though - there should be a little *help* from the author in the form of few tips. For example, is it better to upgrade then buy new towers? (money-wise). I ´ve just tryed the Castle defence map and couldn´t tell at all the difference between water, fire, nature and earth towers. Are there enemys resistant to some of them? any special effects? (which reminds me, authors, better tower descriptions please!). Games created this way are a little bit confusing, but if you repair this issue (and maybe add a speed up button :)), this will revolutionize TD games, since all *normal* ones will be created by it, it will force developers not using this create something much more original. 5/5 definitely! perfect it!