If you ever get around on doing more icons, it's pretty easy to do a script that would replace each SE lotag to another picnum.
This is a non-destructive visual thing that I already did for the SW mapster toolkit.
In my case I used a lot of colour on the icons to make them stand apart too, plus often I removed the backgorund itself.
The system basically allows you replace with any existing picnum loaded in editor, manipulate it's other visuals and even duplicate it (i.e. different dimension text floating on top of the sprite itself).
Example in SW would be that I added a floating "MULTI" text for sprites tagged as multiplayer-only or show enemy spawns visually as transparent "ghosts" together with the actual respawn sprite.
Down the line when I finally get to do more work on the "grand unified duke3d script" I've been working on, the plan has always been to visually indicate stuff like this so I'd definitely be interested on using such if it was made.
I do recommend having a letter in some shape or form as all guides will refer to each sprite by their name.
Even as a veteran, it leaves less second guessing.
SE = Wrench is good
Activator = Button is great
Touchplate = Something that indicates a trap/trip is missing here, first it made me think of speed shoes = gpspeed

Activatorlocked = perfect
Musicandfx = Speaker works, perhaps adding a sound wave or two would be my personal preference
Locator = good, perhaps one suggestion is to have a trail and "X marks the spot" style motif?
Cycler = If doing SE specific ones, maybe I would tie it somehow
Masterswitch = Kind of works, but if doing SE then might overlap with SE13. Masterswitches do a lot more than just SEENINE triggers

Respawn = Works, personal preference is closer to monster, current design looks a bit robot-like (pal doesn't help here).
Gpspeed = While time is related, I feel that I would prefer speed motif than time as this can even determine distance for things like bridges.