What is the naming convention for Powershell functions with regard to upper/lower case usage?

Naming convention can be tricky. While a fixed naming convention may provide aesthetics or simplified usage, it is not required to be followed. In general, a naming convention that I advocate for is the one that is used already in Powershell. As functions are created on verb-noun base, each word starts with a capital letter or if it is an abbreviation - all capitals, or if it is a proprietary - then as it is accordingly.

I have, for example, created some functions for myself:

Get-ServerDiag
Mount-TrueCryptVolumes
Start-RDP
Generate-RandomPassword
Nuke-Environment

You can imagine what these functions do, it is rather clear, straightforward and compliant with built-in Powershell functions. I do however have exceptions which come from "importing" a several Unix commands to Powershell (like killall, pidof etc...) You can always use a Set-Alias if you prefer to write something else.

This question, however important, is discussable as there does not seem to be the 'one, best way'. It is all, in the end, up to personal preferences.