Arguably on of the best custom ROMs aesthetically is MIUI, its clean stylish interface has won it many fans, if you want a piece of MIUI without the need for the whole ROM, you can now install its file browser on any other ROM.
To install it, point your phone’s browser to this thread on the xda-developer website and scroll down to find the MiFileExplorer_v188.8.131.52.apk link.
Click it to start the download, once completed simply click the file name to launch the installer. Once installed it can be run like any other app. While not as full featured as say ES File Explorer, its much nicer to look at. It does also offer a handy FTP server option , so you can copy files to and from your phone using your favourite FTP client on your desktop