I'd need to know more about the room really, but an isosceles or equilateral triangle will be fine.
Take into account though that the closer the speakers are, the more muddled the image can become, so they'll need to be a certain distance apart (6-7 feet usually) in order to get a decent stereo field. This might be the choice if you're listening down the longer length of a very thin room - you don't want the speakers too close to a side wall as in this position they won't be toed in very much, and you may well end up with a lot of HF reflection from the side walls.
An equilateral triangle works well with speakers that are very good at imaging, so this choice isn't good for all speakers. This will more than likely be the choice of those listening across the shorter length of an oblong room. Depending on the speaker's imaging abilities, some may need to be toed in more than others in order to produce a good central image.
In your position, angling them heavily inwards with them being so close together will more than likely leave you with a very mono sounding stereo field, lacking in width. I think you should try them facing straight out if you're quite far from them - even speakers that don't image too well should be able to give a good central image when that close together - unless of course, they're just too close to be able to image well at all.