Ok, most of the BBC coding that you might use can be found across the top of the text box when you make a post (Color wheel for font color, the world for URL, etc) and these can be moused over to find out their use. But there are some that aren't listed across the bar, so here they are for use! These have been confirmed to work, and this list will be updated as more are confirmed.
Though there are many buttons for most codes, here's a list of Official Codes that will work: ProBoards BBC Codes
Image Sizing: To change an image's size, put style="max-width:25%; after the URL of the picture. You can change the % to whatever number you want to adjust the size.
Note: Not all of the Codes will show up properly on the Preview, just as on the old site some characters wouldn't properly show up. So best when putting in a code to Preview, then even if something seems wrong go ahead a post and if it needs editing from there, you obviously can.