All the parks under National Parks are good for taking pictures of models.
that also include Chinese Garden and Japanese Garden, which are under JTC.
you can also go take along Orchard Road, Merlion Park, outside Marina Bay Sand.
not forgetting all the beaches, from East Coast to West Coast, from Lim Chu Kang to Changi Beach, can also go to Siloso Beach.
if too lazy to go too far, can just go down stair HDB void deck can also take very decent photos if you have the skills.