Spell and abilities that can be cast in reaction usually have no spell alert.

Current Counters

Class	Effect	Expansion	Texture
Death Knight	Rune Strike	Wrath	none
Hunter	Counterattack	all	none
Hunter	Flanking Strike	SoD	tooth_and_claw
Hunter	Kill Shot	Wrath	none
Hunter	Mongoose Bite	Era/SoD	none
Paladin	Divine Storm	Wrath/SoD	none
Paladin	Exorcism	all	none
Paladin	Hammer of Wrath	all	none
Rogue	Riposte	all	bandits_guile
Shaman	Molten Blast	SoD	impact
Warrior	Overpower	all	none
Warrior	Execute	all	none
Warrior	Revenge	all	none
Warrior	Victory Rush	TBC/Wrath/SoD	none
Warrior	Raging Blow	SoD	raging_blow

Suggestions

Death Knight

Rune Strike could use bandits_guile at top position, similar to Rogue's Riposte, but with a smaller size to avoid overlap.

Hunter

Counterattack could use bandits_guile at top position, similar to Rogue's Riposte, but with a smaller size to avoid overlap.

Kill Shot could use focus_fire at top position.

Mongoose Bite could use white_tiger at top position.

Note: because Kill Shot is available in Wrath only and Mongoose Bite is available in Era only, both could coexist at the same location without overlapping with each other.

Paladin

Hammer of Wrath could use hand_of_light or denounce (maybe as an option?) at top position.

Exorcism (#209) and Divine Storm (#210) TBD.

Warrior

Overpower could use bandits_guile at top position, similar to Rogue's Riposte, but with a smaller size to avoid overlap.

Execute could use sudden_death at left/right position, similar to Sudden Death, either with a smaller size to avoid overlap, or with normal size to overlap with Suddden Death (Wrath issue only). Maybe the best would probably be to overlap anyway. It might look a bit weird, but it would be even weird-er to repeat the texture with different sizes.

Revenge could use ultimatum at top position, with a small risk of overlapping with Sudden Death (Wrath issue only).

Victory Rush could use dark_tiger at left/right position, with a higher size to avoir overlap and smaller opacity to make it not too visible.

Options

There would be a new option for each of these alerts. They would probably be disabled by default.

Special case for warriors: there are sub-options to glowing buttons so that e.g., overpower effect is seen either in the intended stance to cast it, or in all stances. The same options should be added for their spell alerts too, although it requires players to manually change options two by two, should they want to synchronize both options (which we probably want).