First off, Gtbro1 - that shot of Priest and Titus has been photoshopped.
There is no way that Titus is that tall.
Second, yes there are pros with 24 inch arms.
I site Kovacs (definately) and quite possibly Vic Richards. Have seen both of them in seminars and talked with them up close.
Kovacs arms were immense - and one of my old training partners had 22+ inch arms so before you say I don't know what 22 inches look like guess again. I almost got mine to 20 as well and Kovacs and I are similar in height and I've seen plenty of top bb's over the years so I have a fair idea of relative size.
Kovacs when I saw him - and I asked him to flex his arms etc (which he did) had the biggest arms I have ever seen in person. Can't speak for any other bodybuilders but if anyone had/has 24+ arms then Kovacs did or does.
Thirdly, Priest has got some mighty impressive arms.
But then looking at that pic of Dillett's bicep - it looks like the size of his friggin head. Amazing. Wish I had seen Dillett in person - a true freak of nature (or un-nature if you prefer).