I would be concerned about a light fixture inside the tank? geckos are wonderful climbers, and might wedge in next to the bulb when they want to bask.
hmmm...I went through your viv build link. very cool tank conversion! I would only want to caution about 2 things:
first, dart frogs need a higher ambient humidity, for the most part, than grandis. that might be a little short on ventilation. you might wish to make the screen cutout larger? just a thought.
second, dart frogs are much smaller than grandis. even a terriblis is quite a bit smaller and will need less volume. that example of how to make the background is awesome, but takes up quite a bit of volume in that tank. perhaps it might give your gecko more room if you make a modified version that doesn't remove so much volume from the viv. again, just a thought. grandis are large, active geckos.