The unsatisfying, but mostly true, answer to this is that there isn't much. Individual Republicans and identifiable blocs within the party had platforms more extensive than being antislavery. Many were former Whigs who still believed in a lot of the Whig program of state-aided economic development, the tariff, etc. However, they were in coalition with former Democrats who largely believed in the opposite of all that: free trade, not much state meddling in infrastructure, etc. There's also an internal split over nativism, with former Democrats generally hostile and former Whigs often sympathetic, but with a significant body of ex-Whigs bucking the general trend; William Seward and Lincoln were both pro-immigrant Whigs from way back.

Both wings of the party tried to pull things their way, but in general the GOP settled on opposing the spread of slavery as the one thing that kept them all together in the years before the Civil War. When it looked in the later 1850s like the economy was going to sink again for quite a while, the more conservative (often called Silver Gray) ex-Whigs tried to swing the party into less emphasis on antislavery and more on the traditional Whig platform but the main body of the party was against that.

That said, if you read the 1856 and 1860 platforms they do have a few things that aren't directly related to slavery. This is from the first:

Resolved, That a railroad to the Pacific Ocean by the most central and practicable route is imperatively demanded by the interests of the whole country, and that the Federal Government ought to render immediate and efficient aid in its construction, and as an auxiliary thereto, to the immediate construction of an emigrant road on the line of the railroad.

Resolved, That appropriations by Congress for the improvement of rivers and harbors, of a national character, required for the accommodation and security of our existing commerce, are authorized by the Constitution, and justified by the obligation of the Government to protect the lives and property of its citizens.

Both of those are a little bit Whiggish, especially the second, but the Dems were not diehard opposed to either idea. The Pacific Railroad was basically an accepted consensus at this point and internal improvements specifically of rivers and harbors, and "of a national character" fit comfortably even within quite far right Democratic thought of decades prior. Just where to draw the line would always be in contention, but no less a Democrat than Jackson himself had been in favor of harbor improvements and the South Carolina nullifiers favored infrastructure they deemed sufficiently national. The 1860 platform is, by design, more moderate but still on essentially those lines.

Sources

Free Soil, Free Labor, Free Men by Eric Foner is all about the GOP's ideology before the Civil War.

Prelude to Civil War by William Freehling is the classic treatment of the Nullification Crisis and devotes a lot of attention to what did and did not square with far-right constitutionalisms with regard to internal improvements.