At the top of the list of the characteristics of those pictures I consider to be good is my preference to for straight pictures. That is, pictures which depict the world "as it is". iMo, the characteristic inherent in the medium and its apparatus (aka: conventions, visual language, et al) which separates it from other visual arts is its inexorable relationship to and as a cohort of the real.
Next up, and of equal importance to the preceeding, is the print itself. Inasmuch as the print is a separate thing apart from the referent it depicts, the print must be a beautiful (wide ranging and diverse meaning) object in and of itself. In other words, I may care about what is depicted but I care more about how it is depicted and presented.
Re: a beautiful object. I am not necessarily writing about the technical / aesthetic qualities of the object itself. While a finely crafted print is most certainly a desireable quality, the beauty I am interested in is how the picture maker has framed his/her referent and arranged the elements therein as depicted across the 2-dimensional surface of the print. And, does that arrangement have visual "energy" which gives my eye the encouragement to dance about the surface of the print?
Or, much more simply written, does the print look good to my eye and sensibilities? If I put a print on my wall, will it engage me and hold its visual value over time by allowing and encouraging a dance, albeit with different steps, with each viewing?
Re: meaning. I used to believe that meaning(s) which might be found in a picture was an important and very desireable attribute. However, over time I have come to believe that, at best, meaning is an illusive and ill-defined commodity. Sure, sure, dependent upon a viewer's knowledge and life experience, all sorts of meaning could be gleened from a picture. Where one viewer sees / feels joy, another may see / feel sadness. Where one viewer sees structured beauty and another may see only randomness and chaos.
Other than pure propaganda which is meant pluck at a single string, a good picture is more like a well struck chord which reverberates with musical complexity. And, iMo, that's the beauty of a good picture inasmuch as a good picture reverberates with multiple and even diverse meanings as the viewer chooses to comprehend them.
My phraseology used to describe a good picture has always been that a good picture is one which illustrates and illuminates. That is, good use of the medium's visual language which, in turn, leaves room for a viewer's internalized contemplation.
And that, in a nutshell, describes the pictues I try to make and those made by others that I appreciate.