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I enjoy working the futoshiki puzzles featured here, but I've also been able able to create and solve many "blank" puzzles using the Simon Tatham program Unequal. Simply put, a "blank" futoshiki has no given numbers at the start, just the pattern of inequality signs linking certain squares. This makes for more of a challenge, but by observing the patterns of "chains" created by the inequality symbols one can gradually deduce the correct numbers. The largest size "blank" puzzle I've ever created is 7 by 7. I have quite a few of these, but I've never come across a blank puzzle in an 8 by 8 or 9 by 9 size. Just ordinary 9 by 9 puzzles can be challenging and require plenty of patience. Feel free to share your thoughts on futoshiki puzzles.

At first glance I'd say for any size one can at least create a trivial puzzle with this pattern:

Code:

And you only need the horizontal hints to make this unique. I guess that gives some room to create more interesting puzzles when also introducing the vertical hints, but I haven't tried it.

I'm really not that huge on Futoshiki; Nikoli once published a puzzle with similar rules, though. Like Futoshiki, each number from 1 through the grid's size must appear once in each row and each column; instead of given numbers, though, the clues come in the form of greater than/less than signs (which mean the same thing as they do in Futoshiki) and numbers between two cells (which indicate the difference between the two numbers).

I've only seen it once, and there were only 5 of them, but it was interesting.

Usually the 9 by 9 puzzles turn into greater/less sudokus, so with the 3 by 3 constraint. This decreases the amount of sign clues you have to give and gives it a nicer look.