I need to create a blank 750 x 380px image on my android phone - then paste some images and text onto the blank image. Simple as this sounds - spent over 72 hours searching the Web with no way to this. Pixlr and all other mobile image editing apps can only edit existing images - but won't allow you create new ones with fixed canvas size. Suffice it to say I haven't got access to a computer now and must do this on my Samsung android mobile. Help guys - I'm about to really really freak out.
Don't freak out. That would be silly.
I just tried (for your question) an app named PhotoSuite 4 Free. I was able to start a new project, specify its pixel dimensions and add a text layer. Seems to be what you're looking for.
(Click image to enlarge)