Not the easiest thing, but two ways to do what you want.
1. Bring up the sniffer. Under the Image tab, click on the URL button. This will SORT THE LIST BY URL. Click again to reverse the sort. Now scroll down find the first wanted entry (resize the column if necessary) and click the row (NOT the left checkbox, the ROW ITSELF.) It'll change color. Now scroll down to the last one, hit and hold SHIFT and click it's row. The entire section (not the entire list though) will turn grey. (Holding CTRL will select only those specific rows you clicked on.) NOW select any grey single option box on the left to enable that entire section. The download count will reflect the number of rows you selected. Click Start or Pause to go.
2. Use the Regular Expression area, and sort per above if necessary. Basically: ONLY USE LOWER CASE HERE, and prepend EVERY non alphanumeric character with a backslash. Example: pictures\.google\.com or 1080p\) Either just do this or read up on RE rules. Alphanums are resonable, but all other characters do NOT do what you expect. If confused, always add a \ before the character.
This should automatically select all rows with those characters, the number of rows will reflect your search. Click Start or Pause.
RE's are weird if you've not read up on them. Preface any strange character with a backslash. And for some reason only here, UPPER CASE breaks the search -- that's NOT an RE thing, I don't know what the deal is.
BTW: I've currently got over 3,000 items in my DL list, adding them 10-60 at a time. At 200K per file, it's taken days running 4 threads. Working fine though, even survived a browser crash(!)