Look at the hardback Expanded Edition of "The Gunslinger" Page 7, Lines 28 and 29 to find this quote: "It spoke of a man who might straighten bad pictures in strange hotel rooms." This is not new to the Expanded edition as this same sentence is found in the previous edition of "The Gunslinger", just look in the limited edition hardback by Donald M. Grant (third printing 1998) put in a three book box set edition on Page 14, Lines 16 and 17.  Now go to the story "1408" first put out in the audiobook of "Blood and Smoke" and printed in "Everything's Eventual" copyright 2002.  I refer to the Pocket Books printing of January 2003 on Pages 488 and 489.  On Page 488 Lines 18 and 19 say, "What Mike had noticed at that point were the pictures on the walls."  Same Page, Lines 24 and 25 say, "All three pictures were in glass frames and all three were crooked."  Finally, on Page 489, Lines 5-7 say, "Although he was not ordinarily a fussy nam, he circled the room, setting them straight."  These are exact quotes and considering the finality of the story called "1408", I'd say this is a definitive "Dark Tower" tie-in/reference.

In the short story, Lunch at the Gotham Cafe, Guy, the maitre'd, screams "eeeeee!" in his ranting. The Crimson King does the same from the Dark Tower at the end of the title book.

In the Dark Tower VII, after Susannah woke from her first dream of Jake & Eddie in Central Park after their death, this, in parentheses: "(this is NINETEEN all of your friends are dead). Seems similar in content to what Mike Enslin hears coming from the telephone in room 1408: "This is nine! This is nine! Nine! This is ten! Ten! We have killed your friends! Every friend is now dead! This is six! Six!" The voice continues, shouting different numbers, but curiously enough, the highest number it ever reaches is eighteen.

From Song of Susannah:

it talks of rolands grandfather who went to Garlan to slay a dragon and was to late it says "No, he was to late. The last in that part of the world had been slain by another king, one who was later murdered." King Roland in the eyes of the dragon killed the last dragon in garlan