From the last image you posted, the window says "Bootable: No". From the screenshot you posted of the files on the USB, this doesn't look like a standard bootable OS X USB. For Yosemite, you could try using Terminal (I'm not sure how Terminal would handle the periods and dashes in your USB's name, so here are the instructions if your USB is named Untitled):
Note that this process automatically erases and formats the USB before moving the files (it normally will confirm this with you), but I like to erase it myself before I do this as a precaution.
sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite.app
After the process finishes, I believe the USB is named "Install OS X Yosemite"