Is there any issue with chametz sold to a non-Jew being visible during pesach? For example, if I sell my whiskey, can I keep the whiskey in a glass enclosure in the living room where it could be seen?
There's no problem with the Chametz being visible, per se, as the Pasuk that says you may not see Chametz refers to your own Chametz.
There are however 2 issues that need attention:
If the Chametz is visible one has to ensure that it won't be consumed by mistake. This would be a serious violation of both eating Chametz as well as stealing from the person it was sold to.
The Chametz should be sold with the entire room it's in being rented to the buyer; and entering it would be trespassing. If this is not practical, then the location of the Chametz [cupboard / cabinet] needs to be sold and partitioned off so that it's not accessed by accident.
As a result, the Kitzur Shulchan Aruch says in סימן קיד - דיני מכירת חמץ
סעיף ד: אִם אֵינוֹ יָכוֹל לְהַשְׂכִּיר לוֹ כָּל הַחֶדֶר, מִפְּנֵי שֶׁהוּא צָרִיךְ גַּם כֵּן לְהִשְׁתַּמֵּשׁ בּוֹ, יַעֲשֶׂה מְחִצָּה לִפְנֵי הֶחָמֵץ, וְיַשְׂכִּיר לוֹ אֶת הַמָּקוֹם שֶׁעַד הַמְּחִצָּה, וְיִכְתֹּב כֵּן בְּתוֹךְ הַשְּׁטָר.
So it would seem that even of you sold the entire glass enclosure in the living room, it should still be covered, to make it obvious that it has been sold.
By the way, you would also need to give the buyer free access to the location.