Trinkets for Crystal Scar.

#Trinkets
in Summoner's Rift are based on vision.
Dominion, however, is a very strongly mobility-based map (personal opinion), with the exception of 'bot-lane'.
So there should be a trinket for mobility, a trinket for countering mobility and a trinket for a stationary player.
However, these shouldn't be extra summoner spells, or have an actual combat based effect, and if they do, it shouldn't be too strong.
Similar to the Trinkets in Summoner's Rift.

So here are my suggestions.
Trinket A
Disable a Health Relic, Speedy Gate or Storm Shield for enemies for a few seconds. Upgrade at level 11 for better stats. Upgrade for money (Path A) to make Health Relic to Poison Relic or (Path B) to make speedy gate to ice gate, both for a few seconds and only for enemies of course.

Trinket B
Make the nearest Turret send out a pulse, that deals damage to enemy minions, upgrade for better stats, upgrade for money to deal damage against champions, as well. ( At level 3 it should be able to be used from the end of the fountain range to damage enemies at your tower ; bot lane of course. )

Trinket C
Grants nearby allies and yourself a short movementspeed buff, that decreases over it's duration. Can't be activated in battle. Upgrades at level 11 for better stats, upgrade for money for even better stats.