It is actually very simple to use FontAwesome and add nice icons:
1. Download FontAwesome: http://fontawesome.io/
2. Add FontAwesome.otf to the Files tab.
3. Load the font and set it to whichever controls you like:
B4X:
Sub Process_Globals
Private fx As JFX
Private MainForm As Form
Private Button1 As Button
Private awesome As Font
End Sub
Sub AppStart (Form1 As Form, Args() As String)
MainForm = Form1
MainForm.RootPane.LoadLayout("1") 'Load the layout file.
MainForm.Show
awesome = fx.LoadFont(File.DirAssets, "FontAwesome.otf", 20)
Button1.Font = awesome
Button1.Text = ""
End Sub
The nice thing is that you just need to copy the icon from this page: http://fontawesome.io/cheatsheet/ and use it like any other character. It will not appear properly in the IDE but it will work at runtime.