One good way is to plan your thoughts in the form of a mind-map starting from a broad concept (e.g. places to find storage solutions) and branching the details (e.g. home, food stalls, etc.) . Each details in turn then become a broad concept (e.g. focus on, say, home) from which other details related to the 'new' broad concept can be branched out (e.g. room, kitchen, etc.)
A successful mind-map helps a reader understand your intent of the theme quickly and effectively in the form of visual illustrations using key words, sentences and annotated images.
The objective of the mind-map is to help you analyse and explore the theme as widely and as comprehensively as possible. From which you will also use it to identify potential design needs and opportunities through further research on a specific area you are interested in.
If you do find you no longer use, refer to or consult your mind-map when you move on to, say, needs identification, that makes your mind-map worthless and redundant. Which in turn means you do not understand the purpose of constructing a mind-map in the first place.
It depends on your objective of putting a particular image in your design journal. Make sure you know why you select a particular image and then you will be able to annotate (write notes on it) meaningfully. For example: I need to know I will be comparing the functionality of various pen storage solutions. The (internet) product image research activity thus becomes focused on searching for pen storage solutions: common and innovative ones, quirky and creative types, etc. Then when it comes to annotating them, I can comment on their functionality by comparing their effectiveness, aesthetics appeal, pros and cons, effectiveness, etc...