Default XFce picture viewer on Slackware Linux is GIMP (GNU Image Manipulation Program). Though GIMP is great for picture editting, it is rather strange why Patrick Volkerding compiled XFCE to use GIMP as a default picture viewer? The downsides of GIMP being default picture viewing program for Slackware's XFCE are the same like Xubuntu's XFCE risterroro, you can't switch easily pictures back and forward with some keyboard keys (left, right arrow keys, backspace or space etc.). Besides that another disadvantage of using GIMP are;
a) picture opening time in GIMP loading is significantly higher if compared to a simple picture viewer program like Gnome's default, eye of the gnome – eog.
b) GIMP is more CPU intensive and puts high load on each picture opening
A default Slackware install comes with two good picture viewing programs substitute for GIMP:
Both of the programs support picture changing, so if you open a picture you can switch to the other ones in the same directory as the first opened one.
I personally liked more Gwenview because it has more intutive picture switching controls. With it you can switch with keyboard keys space and backspace
To change GIMP's default PNG, JPEG opening I had with mouse right button over a pic and in properties change, Open With: program.
If you're curious about the picture on on all screenshots, this is Church – Saint George (situated in the city center of Dobrich, Bulgaria).
St. Georgi / St. George Church is built in 1842 and is the oldest Orthodox Church in Dobrich.
In the Crimean War (1853-1856) the church was burned down and was restored to its present form in 1864.
gpicview is another cool picture viewing program, I like. Unfortunately on Slackware, there is no prebuild package and the only option is either to convert it with alien from deb package or to download source and compile as usual with ./configure && make && make install .
Downloading and compiling from source went just fine on Slackware Linux 13.37gpicview has more modern looking interface, than gwenview and geeqie. and is great for people who want to be in pace with desktop fashion