I was a Snow Leopard hold-out as well and just went thru the same dilemma as you after the El Capitan upgrade, and here's what I did to work around it.
Instead of the usual drag/insert a picture or graphic onto a black screen and sizing it as I wanted(or even by itself), I opened the pic/graphic on the Desktop (like you would a screensaver), shot 10 seconds of that with the video cam, imported that in like any other movie, inserted into my project and cut the time length as usual. Done!
Didn't bother setting up a tripod as it was initially just a test, but the slight hand movement of the still pics and graphics ended up being somewhat more interesting to see in the project and in one instance even closed the Mac while shooting the screen while the room was dark and that produced a neat effect of the title falling like a wall towards me,which I'm sure is a transition out there but iMovie never had it, and that one ended up in the final edit as well.
I also tried another method, which I saw online, which was to make a slideshow in the 'Photos' app. First tried it with just a couple pics, then with many, and found a neat optional feature in there whereby the pics would scroll thru the screen sometimes breaking it in thirds and fourths as they slid in together and while I didn't use that effect yet, it is an interesting work around I wouldn't have come across without this problem.
I've read so many bad reviews about updating iMovie to the latest version I think I'll hold out again till there seems to be no other solutions to the next problem. Hope you understand what I suggested above, and best of luck in all your iMovie endeavors!