I would like to start adding place holder art to my game's prototype right now, but I'm stumped. Loading a single image file is no problem at all. My problem is settling on how to store/load animated sprites. I have no clue how this is commonly done. When I finally get around to an artist actually creating some artwork for my game, I'd like to have a system/format that will allow them to easily export it and me to easily import it.

Here's all I've really decided on:

• I don't want to use GIFs
• I would like one object/character's entire set of frame by frame animations stored in a single sprite sheet (to avoid lots of texture switching)
  I was thinking of creating a single folder for each object/character, and in each folder would be a "description.xml" file that would tell my game engine which animations there were for the sprite, which frames correspond to which animation, each frame's duration, the location of each frame in the sprite sheet, etc. In addition to the "description.xml" file, there would be the actual "sprite.png" file that would be the sprite sheet for the object/character. The problem is that in all my googling, I haven't found any kind of tools or plugins that make this easily possible, and I don't really want to roll my own plugins right now because I'm not even to the point of working with an artist, and so if I roll my own solutions I may have to end up completely junking them, thus wasting a lot of time and effort.
  
  What do you think? How are animations and effects normally stored in a game? How can I most easily work with the artist, in terms of making a system that will be (most) convenient for them? Are there any particular plugins for Gimp/Photoshop/Inkscape that I should be aware of?
  
  For what it's worth, I'm using SFML and C++.