Re-preflight on the image assets resulting in 24px tall images in each case. This is done by cutting the top edge close (well into the aliased edge on top.)

Added defs for the horizontal and vertical sliders.

AppKit/Themes/Aristo/ThemeDescriptors.j

@@ -1021,6 +1021,74 @@
     return scroller;
 }
 
++ (CPSlider)themedHorizontalSlider
+{
+    var slider = [[CPSlider alloc] initWithFrame:CGRectMake(0.0, 0.0, 50.0, 24.0)],
+        trackColor = [CPColor colorWithPatternImage:[[CPThreePartImage alloc] initWithImageSlices:
+        [
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-left.png" size:CGSizeMake(4.0, 5.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-center.png" size:CGSizeMake(1.0, 5.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-right.png" size:CGSizeMake(4.0, 5.0)]
+        ]
+        isVertical:NO]],
+        
+        trackDisabledColor = [CPColor colorWithPatternImage:[[CPThreePartImage alloc] initWithImageSlices:
+        [
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-disabled-left.png" size:CGSizeMake(4.0, 5.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-disabled-center.png" size:CGSizeMake(1.0, 5.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/horizontal-track-disabled-right.png" size:CGSizeMake(4.0, 5.0)]
+        ]
+        isVertical:NO]];
+
+    [slider setValue:5.0 forThemeAttribute:@"track-width"];
+    [slider setValue:trackColor forThemeAttribute:@"track-color"];
+    [slider setValue:trackDisabledColor forThemeAttribute:@"track-color" inState:CPThemeStateDisabled];
+    
+        var knobColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob.png" size:CGSizeMake(23.0, 24.0)]],
+            knobHighlightedColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob-highlighted.png" size:CGSizeMake(23.0, 24.0)]],
+            knobDisabledColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob-disabled.png" size:CGSizeMake(23.0, 24.0)]];
+
+    [slider setValue:CGSizeMake(23.0, 24.0) forThemeAttribute:@"knob-size"];
+    [slider setValue:knobColor forThemeAttribute:@"knob-color"];
+    [slider setValue:knobHighlightedColor forThemeAttribute:@"knob-color" inState:CPThemeStateHighlighted];
+    [slider setValue:knobDisabledColor forThemeAttribute:@"knob-color" inState:CPThemeStateDisabled];
+    
+    return slider;
+}
+
++ (CPSlider)themedVerticalSlider
+{
+    var slider = [[CPSlider alloc] initWithFrame:CGRectMake(0.0, 0.0, 24.0, 50.0)],
+        trackColor =  [CPColor colorWithPatternImage:[[CPThreePartImage alloc] initWithImageSlices:
+        [
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-top.png" size:CGSizeMake(5.0, 6.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-center.png" size:CGSizeMake(5.0, 1.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-bottom.png" size:CGSizeMake(5.0, 4.0)]
+        ]
+        isVertical:YES]],
+        trackDisabledColor =  [CPColor colorWithPatternImage:[[CPThreePartImage alloc] initWithImageSlices:
+        [
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-disabled-top.png" size:CGSizeMake(5.0, 6.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-disabled-center.png" size:CGSizeMake(5.0, 1.0)],
+            [_CPCibCustomResource imageResourceWithName:"HUD/vertical-track-disabled-bottom.png" size:CGSizeMake(5.0, 4.0)]
+        ]
+        isVertical:YES]];
+        
+    [slider setValue:5.0 forThemeAttribute:@"track-width"];
+    [slider setValue:trackColor forThemeAttribute:@"track-color" inState:CPThemeStateVertical];
+    [slider setValue:trackDisabledColor forThemeAttribute:@"track-color" inState:CPThemeStateDisabled];
+    
+        var knobColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob.png" size:CGSizeMake(23.0, 24.0)]],
+            knobHighlightedColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob-highlighted.png" size:CGSizeMake(23.0, 24.0)]],
+            knobDisabledColor = [CPColor colorWithPatternImage:[_CPCibCustomResource imageResourceWithName:"HUD/knob-disabled.png" size:CGSizeMake(23.0, 24.0)]];
+
+    [slider setValue:CGSizeMake(23.0, 24.0) forThemeAttribute:@"knob-size"];
+    [slider setValue:knobColor forThemeAttribute:@"knob-color"];
+    [slider setValue:knobHighlightedColor forThemeAttribute:@"knob-color" inState:CPThemeStateHighlighted];
+    [slider setValue:knobDisabledColor forThemeAttribute:@"knob-color" inState:CPThemeStateDisabled];
+    
+    return slider;
+}
 + (CPSlider)themedCircularSlider
 {
     var slider = [[CPSlider alloc] initWithFrame:CGRectMake(0.0, 0.0, 34.0, 34.0)],