To answer your question about little words, if they are part of a sentence, they usually don't have a picture. I almost think this is why ASL is easier for me to understand than spoken language.
So for example, the word but, alone brings the image of a butt (yeah, I know), but if used in a sentence, like I wanted to go to the store, but couldn't, I would likely picture someone walking up to a store and turning back around (at this moment in time, and old general store near me called Anderson's which is now closed with me walking up to it and a closed sign on the door).
Has generally is either someone holding something (like she has a book) or someone having a description (she has blonde hair). Has doesn't have a picture to itself, but in a sentence it is the person/thing possessing something. Are is similar, it could be they are late (people walking in looking at a clock) or they are short (a bunch of people my height).
Some, the and a/an are all sort of number words. Some can be relative (some Americans - thousands, some of my fingers - less than 5) so depends on the subject. Some Americans would probably picture the map of the US with people standing around the states. Some of my fingers, I would picture my hand with certain fingers held up.
I was trying to figure it out while reading a play for homework, whether I hear a voice that narrates the picture or not. I think sometimes there is one, but sometimes there isn't. There are definately sound effects in my head - wind, explosion, and basically all of the onomatopoeia have sound affects attached to the picture. Some are a feeling, like God is a warm cozy feeling, love is similiar, hate is a cold feeling, and of course, things like temperature, pain, sensation are all felt. Taste is also important and ironically not always something that would generally be edible. I don't know how to explain it exactly, but I taste the word cloud. I picture it, but there is a specific taste to it too. There have been times I have gone somewhere and commented "this smells like X tastes" where X is not always something you would normally taste. Now granted, as a kid I had to put everything in my mouth (probably one of the Asperger traits, sensory seeking), so I've probably tasted things most people haven't, but some words have a taste that doesn't make sense. Or a texture on my tongue, like silver is a cool, smooth, shiny taste.
So...do I hear a voice? Sometimes I think I do, but if for example, I'm listening to a book on tape, and NOT reading along (normally I do both for full comprehension), I cannot repeat back to you a quote of the words most of the time, but I can usually repeat back to you the picture I saw. I remember what people say in pictures. I remember places by pictures. But I think sometimes there is a voice that narrates things. I know when I was little, a lot of times I would talk like I was writing a book. Rather than saying "Jimmy told me that he can climb a tree." I would say, "I can climb a tree," claimed Jimmy.