I don't know of any best practices guides on subnet and VXLAN assignment but if you are looking to set a standard within your team or company you can come up with something that makes sense logically.
Personally if you are talking VLANs in the thousands I would move to the 10.x.x.x private range and only use VLANs in increments of 10
Starting with VLAN 10
10 - 10.0.1.x
20 - 10.0.2.x
...
...
990 - 10.0.99.x
1000 - 10.1.0.x
This would give you 99 VLANs in the range of 10-990, then increment the 2nd octet and start again in the 1000 range.
Each time you increment the 2nd octet it would give you another 100 VLANs to use and if you go up to 10.255.100.0 that would be 25,600 VLANs that you could use all logically segmented, which seems like more than you would ever need.
Here are some examples
10.15.25.x - VLAN 15250
10.0.15.x - VLAN 150
10.255.97.x - VLAN 255970
You could even break those /24 subnets into smaller ones and fill in the other subnets in the range from 0-9 adding even more VLAN possibilities.
If you are dead set on using the 172.16 range then you could use a similar method but it wouldn't be as obvious just by looking at the subnet or VLAN id
Hopefully this has been helpful or at least gave you some information to consider to come up with a system that works for you.
