mynameisjon1988 if you do not have PSP you can use a free program called XnView found HERE
XnView is a utility for viewing and converting
graphic files.
It has the features :

Import about 400 graphic file formats
Export about 50 graphic file formats
Multipage TIFF, Animated GIF, Animated ICO support
Image IPTC, EXIF metadata support
EXIF auto rotation support
IPTC editing
Resize, rotate, crop support
Lossless rotate & crop (jpeg) support
Adjust brightness, contrast...
Auto levels, contrast
Modify number of colors
Apply filters (blur, average, emboss, ...)
Apply effects (lens, wave, ...)
Fullscreen mode
Slide show with effects
Batch convert, batch rename
Create WEB page easily
Screen capture
Create contact Sheet
Create or edit Multi-page file (TIFF, DCX, LDF)
TWAIN & WIA support (Windows only)
Print support (Windows only)
Drag & Drop support (Windows only)
Compare image side by side
Filmstrip layout
44 languages support (Windows only)
And many many other things...
No Adware, No Spyware

After opening XnView & selecting the folder you have your wall in, righclick on the wall & select set as wallpaper...choose either fit to desktop or best fit to desktop...check which one works best. I have done this with a # of walls & it works great.
Just to note you can also increase the thumbnail size of your images including those on your folders, found under tools...options...browser...thumbnails..appearance...You can also change the background & thumbnail color as well.... one of my most favorite features of this program.

It's My Secret