Short Answer
There really isn't one. There are certainly some general norms that you'll find among people's pedalboards. You'll usually catch tuners before EQs, EQs before drives, and drives before time-based effects. However, there's nothing to be afraid of when ordering effects one in front of another.
Long Answer
So, unlike powering your pedals, there's no harm in mixing and matching certain effects in a signal chain. While pedal power has some hard-and-fast rules, breaking or sticking with traditions on signal chain order have no greater ramifications to sweat. Like we said, there's plenty of norms that can be followed or broken when it comes to designing the flow of your pedalboard, so truly, it's up to taste.
When you see pedalboards out in the wild, there will always be elements of choice and customization visible. For one, do they stick with the norm of having your drives before your time-based effects? Do they put their tuner at the very start or very end of the chain? It's no big deal to assemble your pedals in a way that sounds good to you – tradition be darned. All your missing out on by ordering your effects one way is the knowledge of how they sound another way.
Some usual rules of thumb when it comes to ordering effects, if you're looking for them, is for one, to put your drives before your time-based effects like modulations and delays. Most players prefer to repeat your dirts rather than dirty your repeats. Another is to place your tuner at the very start of your chain to get the best read of your signal incoming to most effectively tune your instrument. You'll likely catch on to other commonalities among pedalboards just by seeing them in action, so keep your eyes peeled, your pedalboard free, and your mind open to any weird idea or possibility that might sound good to you.
