I think "we've got ourselves..." generally sounds more excited or dramatic than the other ways of saying it. That's just my impression, though.

Well, well, folks, looks like we got ourselves a tough question to answer. I agree with the other answers... Just another way to say "we have" to make it more dramatic of a tone.

We have got ourselves something means the same thing as we've got something for ourselves, or more simply, we've got something. The word ourselves is used idiomatically for emphasis. It can also imply that we have caught something or someone important or surprising. In the examples you gave, we have got ourselves something has a connotation of sarcasm or irony. The speakers are not happy or excited about what they have got, but rather annoyed or amused by it. For example: We got ourselves an alien remodeling a pyramid. (The speaker is sarcastic about the alien's activity and implies that they have to deal with it.) We've got ourselves a new screen saver. (The speaker is ironic about the computer's malfunction and implies that they have to fix it.)

It's hard to explain but it's usually said in a certain tone when you're announcing something--perhaps something surprising or slightly unexpected--to an audience. "Well, we just got ourselves a brand new truck." (When the truck fell unexpectedly into their hands through chance circumstance) "We've just got ourselves another mouth to feed" (When realizing your wife has an unintended pregnancy) "We've got ourselves a big problem on our hands" (When everything was expected to go well)

Like this? -We have got ourselves something amazing to show you -We have got ourselves something that's extraordinary -We have got ourselves something in common