It will be your next problem though as loading from a file can significantly slow down your frame.
Load both textures before the loop and then set the sprite to the texture you want to use before drawing it. This is the option closest to your current design and allows the two image files to be left as they are.
A better option, though, is to place both the textures into one image file and load it as one texture (before the main loop). Then, for each tile, just set the texture rectangle to cover the part you want to use. This can also significantly increase performance even over the previous version.
Better still, use a tile map object, which will be a single vertex array that draws all tiles in one go. This will also require the tiles to be in one image.
A simple example of this is available in SFML's vertex array tutorial:
https://www.sfml-dev.org/tutorials/2.5/graphics-vertex-array.php#example-tile-mapIf you need more flexibility, you may want to create your own vertex array or use something like Selba Ward's
Tile Map, which does it all for you