Well the fella in that second picture is wearing his flashes half way down his calf. At this point their not serving their intended purpose of holding up the hose. And they look odd.

He also appears to be wearing his kilt pin on the wrong side.

I get wanting to break the mold a little, but there's good reason to follow advice from the fellas here. Whatever level of formality you choose - as you say it varies for the ceremony - I'd recommend dressing well as it applies to that level. If you go black tie level, adhere to black tie norms. I know the times I've done otherwise, I regretted my appearance later