These are very nice. Good job experimenting different angles and motion with loose lines. I know what you mean by imagining more complicated shapes being difficult. I realized at some point that lack of imagination was not the problem, but lack of knowledge, so I didn't know how. For me, spending time studying references helped, just looking at pictures and finding inspiration and ideas - what you've done here with a fox :). Do more of that. Another thing that worked for me is experimenting with lines and shapes. Just scribbling something without knowing what it will turn out to be, if nothing. There's a good chance, though, that you accidentally draw a shape that reminds you of something, and just like that you discover a solution to a problem. Besides, drawing without purpose, or set goal, on occasion is increibly relaxing :).