I realized that was a poor explanation, what I do is this: I have the sprite sheet.png (you can view this in "recursos/imagenes" folder) and I load it on Tiled. I use Tiled to create the map, and then export it to .txt. Afterwards, I delete some things (like headers for example) that are present on the exported .txt, but I don't want and therefore my custom loader doesn't recognize.
The tiles(rectangleShape) are loaded (tile size is dependant of the game resolution) one by one, and then I apply the correspondent sf::Texture to each. Actually, it's the same texture (the sprite sheet) but rectanlgeShape has a method (setTextureRect) that lets me grab only a portion of the sprite sheet.
Unfortunately, there's a bug (I think it's related to the sf::view, and not the sf::rectangleShape) where one line of pixels will load wrong, and so you end up with a line of wrong pixels on your texture. This is a known issue and they will fix it (I hope) for SFML 2.X. In other words, won't be fixed for SFML 2.0