Let me start by explaining what I think of as "everyday magic". I am talking about the low level, low cost spells that can be cast by almost anyone. For Mer, these could be quite powerful, since they seem to be a more magical race with a higher level of natural magika. Even for Men, these little cantrips could be quite useful, and maybe even provide an alternative to more technological methods. For instance, instead of matches, what if everyone could cast a mini-fireball to start campfires in raging blizzards. Instead of relying on advances in medicine, nearly everyone could heal scratches and scraqes, without fear of infection. Tamriel seems to be a very "magical" land, and nearly everyone seems to have some magical ability. A random thief in the Imperial city dungeons can cast a fireball strong enough to kill a rat. Even in Skyrim, where magic use is frowned upon, an escaping prisoner knows some healing magic.
For gameplay, we we are limited to the big, impressive, world shaking spells, but what else could magic be used for, and how would it affect a culture? For example, "summon almost-invisible friend" would make many children's game more fun, and "static discharge" could be used to chase small animals out of the house. "Change hair-color" would be very useful for that party at the castle. Or do you think magic is more limited and restricted for some reason?