Translation:These beautiful pictures are on the wall.
Present tense indicative mood 3rd person - wow, that is VERY specific. So, to relate what you're saying to the sentence, "szép képek" is an adjective/noun combination, so you can't use "vannak," because it's in the present tense, indicative mood and 3rd person? Whereas "fal" is just a noun, so you can (or maybe have to?) use "vannak" with it?
Thanks for the answer!
It seems you're a bit confused.
Ezek szépek. = These are pretty.
Ezek képek. = These are pictures.
Ezek a falon vannak. = These are on the wall.
"Szép" & "kép" are just adjectives/nouns. "Falon" conveys an adverblike meaning, so you use lenni. The sentences above are the only valid possibilities (except for changing the word order & using synonyms, of course.)
Regarding the original sentence, it says that these pictures are somewhere (adverb), while your translations says that "these" are something (noun in this case, but could be adjective.)
Oh, right - you need to use lenni when talking about something being in a location. I've learned that rule, but I guess I wasn't thinking of it when we had this conversation. But it also sounds like "being in a location" is part of a larger category, adverbs (or an adverbial phrase).