alguno vs algunos, alguna vs algunas

Question

There seem to be a lot of confusion around this subject. especially when using the word 'some.'Could you please explain the difference illustrated in these two examples.Tengo muchas postales de Venecia,
¿quieres algunas?
I have many postcards from Venice, do you want some?

He imprimido nuestras fotografías del viaje, ¿quieres ver
alguna?
I have printed the pictures of our
trip, do you want to see some?And just as an aside, the sentences in English should be separated by either a semi-colon or a period, not a comma.  When a comma is used to separate two independent clauses, it's called a comma splice or a run-on sentence.  I'm not trying to be a know-it-all.  This is in the spirit of having the best grammar.

Answer

Hola Sherri, 
The second big box in the lesson is explaining this difference, where it says "but be careful..."
but I will try to explain again with these two examples:
The first one asking if he wanted some [postcards] is using "algunas" in plural because the speaker means "some of those postcards, plural, so he is offering "a few".
The second one, despite talking about "nuestras fotografías", a clear plural reference, when asking if he wants to see some, he is using "alguna" in singular, meaning "one or two, the odd one" (as if softening the plural meaning of algunas, maybe to make the idea of seeing photographs sound more appealing)
I will pass your comment about the use of comma in English to our native English team. Gracias.
Saludos,
Inma