Ayf, I think a lot depends on the overall space and the style of the sofas. Can you share a photo?

Do you mean abutting in a corner? I think it is nice to pretty much fill the space but it's not necessary.

I have an end table (26") there and it looks fine. I would think you'd want a table and lamp there.

I need a table next to every seating choice for drinks, books etc. so yes, I think you need one.
I would let the scale of the sofas dictate the size of the table- you don't need to fill up the entire space, just occupy it.

Here's what the space looks like. Obviously the end table there is way too small.

The couches are a queen sleeper and a 109" non pullout so they look fairly large

I think, in this case, height is going to be more important than size. You need a much taller table.

do you have any recommendations as to what height or kind of table would go well here? we're really bad at decorating :(

The height of the end table should be the same height or within two inches of the height of the arm of the seating.

Check sites like Overstock -- but first measure the whole space -- including height.

Also -- could you place a lamp (table? or standing?) at that spot to add warm light to the seating area?

Yes - higher, and bigger. If the space is 36", look for a 30"-32" square table. I'd also use something other than glass.

Something with two levels, so it doesn't look massive, and can hold a stack of big books and/or a pretty bowl - something to make the corner nice to look at when you walk in.

And a low, fat lamp...high enough to send light over your shoulder when seated, but not high enough to be in your sight lines when you come into the room.

Something along this line, in a style that works with your things:

I have gotten IKEA dining tables in the 30-32' square sizes that they sometimes have, cut the legs to the desired height and painted or stained them to suit--if budget is an issue.