imageplane tool for 3dmodelers.
its really not so easy to select/zoom/rotate/locate reference images while 3d modeling.
but in Referencetool, its easy.

if you wanna read boring sentences continue or watch 2 minute tutorials if you wanna form an opinion:
2 Minute Tutorials for Reference Image Tool on Youtube

select/zoom/rotate/pan picture is easy, no waste space,
very useful for 3d modelers while modeling in any 3d kind of application. Features:

• Fast Selecting Reference Picture .
• Ghost Mode Functionality.
• Zoom / Flip / Pan / Rotate On the Fly.
• Multiple Frames
• Save/Load Workspace. (Restore Last Workspace)
• Drag Drop From Web Browsers / Multiple files from local pictures.
• Win7×64, Win8.1×64, Win10×64 compatible

its resizable in all corners of window so you can stretch, fit double click works similar to photoshop. by the way you can open reference picture. hold spacebar to move window. greater less keybutton to toggle the window:from active to ghost, ghost to hide, hide to active again.
left and right key buttons to flip picture. or right mouse button flips reference picture too. mousewhell for zoom in and out.
middle mouse to reset position, zoom and rotation. control + mousewhell or control + mouse drag you can rotate.
Update 2.7 (Aug/13/2017)
- GhostMode/Off/On shortcut key changed from ’< ’ (Less/Greater) to INSERT button. - Changing transparency value to zero had a disappear bug for all windowses. fixed. - Windowses goes backward bug. fixed.