The worst enemy of creativity is the feeling that everything has been done already. So, quite often all starts to look like a repetition of old tricks. Then the solution might be to repeat a bunch of them at the same time.
However, on photo editing it is important to find out and learn what would be the best possible order to do things, to achieve the desired outcome. For example vignette is probably best added in very beginning of the process to give the whole image the same look when something else done. Sharpen on the other hand, usually should be done as a very last stage.
Lately I have played a lot with PicSay Android photo editor. It is fun way to spend time, sitting relaxed on an armchair, and play around with effects. PicSay also just got a new update, which makes it much easier to use, and also gave some new tools to try. Then combining the effect available on editor, and the post processing art filters available on camera software, it is possible to get even more interesting results.
A very nice camera mode what I have used lately is a 'Poster mode' available on Vignette Android camera software. It give bright "posterized" colors and sharp outlines even in very dark conditions. Then that can be used further on as a post processing material. For example 'Comic print' filter on Picsay makes the picture look like heavily enlarged raster image.