I created a custom graphic in Inkscape, a very simple 30x30 pixel box with a blue fill and 1-pixel black stroke, and the word "if" in text in the upper left corner. I removed all whitespace from around the box, then saved as "Inkscape SVG."
When I import it into yEd, the "if" text is missing, but everything else acts normally. The box is blue, there seems to be a black line around the outside, and it resizes/scales just fine. I need the "if" in it, though, and it's killing me trying to figure out what's up.
I will try to upload the .svg file I created, and a screenshot of the result in yEd. (NOTE: The forum didn't like the .svg format, so I exported in .png, so you get the idea.)
Now here's the screenshot showing an expanded node, without the "if:"
Let me know if you need anything else. Thanks in advance!