Hi There,
My personal experience I share here.
When I re-design/design (and I do not have the services of an agency with UI designers for my client - usually large corporates) I usually do the following:
I look at Google like this
(Example Link)
then I pick an image that I like and visit that website
(Example Link)
I also make extensive use of Pinterest and search for UI Design - and there are plenty of ideas as well.
Using PowerPoint or Gimp, I create my icons, graphics, headers, footers, backgrounds and splash screen to incorporate into my app as per the direction I have chosen.
Hope this helps a bit.
Enjoy !!