I've been working on designing a Gui, and I find it hard to create complex, good looking Guis by using Frames and Text, so I used Gimp and made a simple one.
The only problem is that ROBLOX's Decal system is really stupid. Can't upload in GIFs, and PNG/JPG/BMP don't have transparency. So how can I create an Image, and load it transparently into an ImageButton.
Also, relating to this but on the Lua side of things, how can I use UDim2 and Tweening on an ImageButton?
PNG does in fact support transparency, I use it all the time. You need to set the frames transparency to 1
Also, you tween Image buttons the same as every other frame, with :TweenPosition() or any of the other tweening methods. http://wiki.roblox.com/index.php?title=Tweening
Since ColdSmoke replied regarding transparency, I'll go into depth about tweening
UDim2 is basically telling the GUI where to move on the screen. I'm assuming you already know how to design GUI's, so look in the position of the GUI. The 4 numbers. To change the position of this you would example.Position = UDim2.new('0,0,0,0') The numbers look kind of like your position, right? That's how you move GUI's.
If you wanna get fancy you can use TweenPosition, this is like UDim2 but moves the GUI smoothly to that part of the display
It's almost the same, instead of doing example.Position it's example:TweenPosition(UDim2.new(0,0,0,0))