Learn Hardcore Spanish (Spain): Cuando miro las fotos, cada recuerdo trae una emoción distinta. - When I look at the photos, each memory brings a different emotion.

Spanish often uses the present tense to talk about habitual or general actions, similar to English: "Cuando miro las fotos" means "When(ever) I look at the photos", not one specific time in the past.
If you wanted a specific past situation, you’d change both verbs:

Cuando miré las fotos, cada recuerdo trajo una emoción distinta. – When I looked at the photos (on that occasion), each memory brought a different emotion.
Cuando miraba las fotos, cada recuerdo traía una emoción distinta. – When I was looking at the photos / Whenever I used to look at the photos, each memory brought a different emotion (past habitual or background).

Why is the indicative (miro) used after cuando, and not the subjunctive (mire)?

Cuando takes the indicative when the action is seen as real, habitual, or completed (present or past):

Cuando miro las fotos… – Whenever I look at the photos (this really happens).

It takes the subjunctive when the action is future or uncertain:

Cuando mire las fotos, te llamo. – When I look at the photos (in the future), I’ll call you.

In your sentence, looking at photos is a regular, real situation, so miro (indicative) is correct.

Why is there a comma after fotos?

In Spanish, when a subordinate clause like Cuando miro las fotos comes before the main clause, it’s standard to separate them with a comma.
So:

Cuando miro las fotos, cada recuerdo trae una emoción distinta.

If you reversed the order, you normally wouldn’t use a comma:

Cada recuerdo trae una emoción distinta cuando miro las fotos.

Why is the subject pronoun yo omitted? Could I say Cuando yo miro las fotos?

In Spanish, the verb ending -o in miro already tells you the subject is yo, so the pronoun is usually dropped: (Yo) miro.
You can say Cuando yo miro las fotos, but it adds emphasis on yo, as in “When I look at the photos (as opposed to someone else).”
The neutral, most natural version is without yo: Cuando miro las fotos…

Why is it las fotos and not just fotos, since English can say “when I look at photos”?

Spanish uses definite articles (el, la, los, las) more often than English, especially when talking about things in general that are still somehow specific in the speaker’s mind.
Las fotos suggests the photos you know or have, not just any random photos.
You could say Cuando miro fotos without the article, but it sounds more like “when I look at photos (in general, not specific ones).” In context, las fotos is more natural if you mean your particular photos.

Why is it cada recuerdo trae with a singular verb, even though “each memory” feels plural in meaning?

In Spanish, cada is always followed by a singular noun and takes a singular verb, just like in English with each:

Cada recuerdo trae… – Each memory brings…

Even though you’re thinking of many memories altogether, grammatically you’re talking about them one by one, so trae (3rd person singular) is required, not traen.
You’d only use the plural with something like todos los recuerdos traen (all the memories bring).

Can traer really mean “to evoke” or “to bring about” feelings, not just physically “bring”?

Yes. Traer is often used figuratively in Spanish, not just for physically bringing objects.
Here, cada recuerdo trae una emoción distinta means each memory brings with it / causes / evokes a different emotion.
Other common figurative uses:

Este trabajo me trae mucha satisfacción. – This job brings me a lot of satisfaction.
Esa canción me trae buenos recuerdos. – That song brings back good memories.

Why is it una emoción and not un emoción? I thought many -ón nouns are masculine.

Many -ón nouns are masculine (e.g. el balcón, el corazón, el avión), but emoción is an exception: it is feminine: la emoción, una emoción.
You have to learn the gender of each noun; endings are only general patterns, not guarantees.
So you must say:

la emoción, las emociones, una emoción, muchas emociones.
Using un emoción would be incorrect.

Why is it distinta and not distinto?

Adjectives in Spanish agree in gender and number with the noun they describe.

emoción is feminine singular, so the adjective must be feminine singular: distinta.

Other examples:

un recuerdo distinto – a different memory (masc. sing.)
recuerdos distintos – different memories (masc. pl.)
emociones distintas – different emotions (fem. pl.)

Is there any difference between distinta and diferente here?

In this context, distinta and diferente are practically interchangeable:

…trae una emoción distinta.
…trae una emoción diferente.

Both mean that each memory brings a different emotion.
In everyday speech in Spain, distinto/a and diferente are both very common; any nuance difference is minimal here.

Could I use sentimiento instead of emoción? What’s the difference?

You could say …trae un sentimiento distinto, and it would be correct.
Nuance:

emoción tends to refer more directly to emotional reactions, often a bit more immediate or intense (joy, sadness, nostalgia, etc.).
sentimiento can suggest a more enduring feeling or inner state (affection, resentment, love, hatred, etc.).

In this sentence, emoción is slightly more natural because it fits well with the idea of memories triggering emotional reactions, but sentimiento is also acceptable.

Why doesn’t cuando have an accent (cuándo) here?

The form with an accent, cuándo, is used in questions and exclamations:

¿Cuándo vienes? – When are you coming?
¡Cuándo aprenderás!

Without an accent, cuando is a conjunction meaning when that introduces a clause, as in your sentence:

Cuando miro las fotos, cada recuerdo trae una emoción distinta.

So here it is correctly written cuando without an accent.