Is there a "conventional" configuration for mounted accessories?
For commuting with panniers and/or a toddler seat, I've settled on the front fork for the D-lock, mainly because little else fits there and I'm restricted by cables and tube diameters elsewhere. Having that 1.5kg forwards also helps the handling with a heavy back load. Don't forget that a heavy lock is only around 2% of a rider's weight - it has to be a long way from the centre of mass to be noticeable for handling. 

A cable lock will often fit in a spare bottle holder. I actually use the down tube holder for this, and the seat tube  one for my bottle. But I'm usually in stop-start conditions (for longer rides I use both bottle holders for bottles). 

My pump actually fits under the down tube with around 10mm clearance to the mudguard. 

My puncture kit (including for humans) and other tools go in a small triangular bag in the front of the frame. A saddle bag doesn't fit with the toddler seat. I'm lucky in that I normally lock up somewhere I'm happy to leave tools and lights on the bike. 

As for convention, if there is one I ignore it. Personal preference combined with quirks of bike design are much more important.