There is a set in size for true tiles which are 1 1/4" and now a 2x2 inch square version. The 2x2 has openlock which are openforge compatible with Devin's changes in creating openlock terrain. As requested, I have also added an integrated true tile with the base integrated for openlock. Look at what size you need for your tile system before printing.
If you need the matching base for true tile size, hero's hoard has it for free at the following link. http://www.heroshoard.com/true-tiles/
There are two add on pieces. One is a regular grate and the other is a destroyed grate with pieces upward as if something escaped. The grate will print out straighter than I have it here, You may want to bend the grate after printing to get a more forced open look. It was not set up that way even though it would be possible because I wanted to have it print without supports. Of course, another option is to just print the original grate and cut your own hole and get the look you want.
To make the optical illusion of the pit, you need to paint each step a darker color with the darkest color at the smaller bottom square. This picture doesn't do it justice. After painting each step from a lighter color to a darker color at the bottom, at each corner going inward diagonally paint a line, thicker at the top and thinner and disappearing at the bottom.
Wyloch or true tile size of 1 1/4" and inch tiles are both available. Resize the grate to get the appropriate size for your tiles.