Veo muchas señales nuevas y las fotografío para mi clase.

In Spanish, when you replace a previously mentioned noun (here señales, feminine plural) with a direct-object pronoun, that pronoun (las) goes immediately before a finite verb (like fotografío). So you say las fotografío (“I photograph them”).
Yes—if you want to keep the noun, you simply say fotografío las señales (“I photograph the signs”). You cannot combine them into las las fotografío; you either use the pronoun or the noun.

Spanish orthography requires an accent to:
• Mark that the i is the stressed syllable (hiato) in the sequence -fio.
• Break the usual diphthong io into two separate syllables (fí-o) instead of one.
Without the accent, fotografio would be pronounced fo-to-GRA-fio (stress on gra), which is not the correct form of the verb.

1. Agreement: señales is feminine plural, so muchas must also be feminine plural. muchos señales would be masculine.
2. Word order: Quantifiers and determiners (like muchas) typically come before the noun. Descriptive adjectives (like nuevas) normally follow the noun.
3. Nuance: You can say nuevas señales and it’s still correct, but it often emphasizes that these signals are “new” as part of a set, whereas señales nuevas simply describes them as recently installed or unfamiliar.

• mi (no accent) is the possessive adjective my (mi clase = my class).
• mí (with an accent) is the prepositional pronoun me (e.g., “para mí” = for me).
Here you are saying for my class, so you don’t accent mi.

Use para to express purpose, goal or recipient: photographing the signs for my class (in order to use them in class).
Por would indicate cause, exchange, or movement through, none of which fits this meaning.

Spanish often uses the simple present (veo) to express both “I see” and “I am seeing.”
You could say estoy viendo to stress that it’s happening right this moment, but veo is more concise and perfectly natural for describing what you see now or regularly.