Not greeting cards but I thought I'd use this technique on some graphics I'm currently developing for my branding. Going to use these in some social media posts as well as maybe some print collateral if I get around to selling my artwork physically.

Original; no filters, just used masking to hide some text with the plant:

Secondary; used Hue/Saturation, Brightness/Contrast filters to change colour of imagery, tweaked opacity and changed colour of text:

Third; went back to simple white with text, kept opacity as it adds a nice variation to the imagery. Desaturated the plants to look how it would look monochrome:

Fourth; reversed the saturation and enhanced it to give the plants more life, everything else is fairly similar to 3 as I just wanted to refine. Might add colour to the text as in 2nd as it fits my brand colour scheme more and the image could use a colour pop:

Fifth; little bit torn between 4th and 5th as to which I appreciate more, one of these examples I will use for some social media platforms in the end. Having multiple variations allows options and also promotes more development in the future if I ever want to change colour schemes:

Conclusion:

Thanks again for the class. I'm slowly burning through your classes and really appreciate every single one. Providing these simple techniques in such a great teaching format has really helped to expand my toolset, but also my knowledge of Photoshop is slowly increasing each lesson I take. Thanks Geni!