The above is from Sinfest, a comic about ...well you have to read some of it.
The point is here that the nativity scene is grossly misinterpreted by a well meaning girl. Cute, right?
She isn't really farther off than you are.
Let's just do a little analysis from the text and from history.
Manger - Luke may have had in mind the Greco-Roman house plan, given that his audience are certainly non-Palestinians and that is the type of house they would have been expecting. If so the manger was an area in the middle of the compound, a small depression where at times grain was threshed and at other times the animals slept. However, that was not the floor plan typical of a home in Bethlehem, which was far simpler, consisting of one large room (usually) and an outer walled area with steps or a ladder leading to the flat roof. The "manger" was probably that walled area, open to the elements but shielded from the wind. Yes, the straw covering might have been there, but the manger refers to the area, not a specific object. Think of it more as a fenced in front yard.
Inn - The New Testament uses all kinds of words that get translated as "inn", the only one that would fit our description of a public building with rooms rented out is found in the story of the Good Samaritan. Here the word is kataluma, or guest room. Joseph had relatives in Bethlehem, we can assume if he is going there to be taxed, but all of them were full, so they had to sleep outside.
Who was there? - Mary (obviously), Jospeh, the midwife(-wives?), the people staying at the house, the neighbors, etc... Baby birth can be a noisy affair, and since we are not told what time of day Jesus is born (we only assume 'night' because of the shepherds) it could have been the middle of the day and half of Bethlehem might have been looking. Hopefully someone kept the animals away. Would your mother have wanted a goat in attendance? (No cows, cows are the luxury models of the domesticated livestock world.)
Time of Year - Spring. Has to be spring. Shepherds do not watch the flocks in the field at night in the winter, they put them in an enclosure. They do watch them at night during lambing season. Spring time. And it suggests the metaphor of the Lamb being born.
Angels - Angels are not pleasant things. There is a reason that the first thing they always say is "Do not be afraid." These are supraterretrial beings unlike anything in the human frame of reference. The Prophets often depict them as having multiple wings and faces. You want to know what seeing an angel is like? Read Lovecraft. Basically only Mary ever had pleasant chat with an angel. Angels do not sing, they might, perhaps, chant; but their main purpose is to deliver messages and kill people. Ask the first born of Egypt.
Shepherds - Yes, they showed up. You can keep them.
Wise Men - Nope. Read the passage in Matthew again. The wise men show up around the time Jesus is 2. You don't come from the "east" overnight. Who were they? Kings? Nope. That tradition starts in the middle ages based on teh cost of the gifts they bring. Three? Nope. That too is based on the gifts, three in number and thus the minimum you need in a play to bring them is three. They are "magi", sometimes given as astronomers/astrologers which is apt given the star gazing, but the same word is more closely rendered in English as magicians or wizards.
So, we have been getting it wrong for years....
Maybe there is something to the idea that we all see the coming of Jesus a little differently. Maybe somewhere between your grandmothers nativity set and the devil girl's birth of Jay-Z you can get it right, right enough so that means something to you.