Use this browser to look for textures or flats. On the left you have the list with your Texture Sets. The list also contains a set named "All" which, obviously, contains all textures or flats. A Texture Set for each loaded resource has also been added. This is useful if you know in which resource the image resides. Once you have chosen your Texture Set, you can use the text field at the bottom to enter the texture name. You only have to enter the name partly and the list of images will adjust to show only the images that match with the entered name. Select an image to view its dimensions at the bottom. When the focus is on the images list, you can press the Tab key to jump between the same image in the "Used textures" and "Available textures" areas. Doubleclick the image or click OK to make your selection or Cancel to close the list.
To make your own Texture Sets, see the Textures tab on the Game Configurations Window.